Last year: 7th
Captain: Simon Harmer
Coach: Anthony McGrath
Overseas players: Adam Zampa, Mohammad Amir
In a nutshell: Last season was bleak: two wins in 11 completed games, playing a brand of T20 last seen in 2007. But this year there are reasons for optimism: Zampa and Amir are around for the whole tournament, while Cameron Delport is a canny signing on a non-overseas, T20-only deal. Varun Chopra is on loan at Sussex for the Championship but back for the Blast, and was the anchor last season with 503 runs at 38.69, while Harmer - who impressed with the ball in the Mzansi Super League - takes over as captain.
Star: Mohammad Amir was a resurgent force for Pakistan in the World Cup, after two tough years following the Champions Trophy, and was a handful at both ends of the innings in 2017 with a strike rate of 20.3 and an economy below seven.
One to watch: Cameron Delport looked set for the wilderness when his domestic franchise Dolphins released him in 2016, but he has carved out a career as a fast-starting opener and is a permanent fixture of the T20 scene: from last July to this April, he played more games than anyone else (56). He crunched a 60-ball 117 not out for Islamabad in the PSL this year, and will make use of Chelmsford's small boundaries.
Verdict: The only way is up
Last year: 6th
Captain: Colin Ingram
Coach: Matt Maynard
Overseas players: Fakhar Zaman, Shaun Marsh, Mitchell Marsh
In a nutshell: Fizzled out last year despite captain Ingram's runs and a fifth consecutive heist at the Oval, while the loss of Aneurin Donald to Hampshire leaves a gap at the top of the order. The Marsh brothers are not the most inspiring pair of overseas signings - not least with Shaun injured and Mitchell in Australia's preliminary Ashes squad - but Zaman has fond memories of Cardiff after the Champions Trophy two years ago.
Star: Ingram has churned out runs against both spin and pace since signing in 2015, and is particularly strong against anything full. His consistency was finally rewarded by an IPL gig with Delhi Capitals, although he underwhelmed coming in later than he is used to. He scored more than 20 percent of Glamorgan's runs off the bat last year, and needs another 400-run season if they are to reach the knockouts.
One to watch: A video of Dan Douthwaite in the nets attracted hundreds of thousands of views over the winter, which showed him reverse-ramping a ball into his helmet and collapsing as though he had been shot. He'll hope to go viral for the right reasons in the Blast; he signed a county deal after impressing for Cardiff MCCU, and slammed a 35-ball 52 not out to win a televised One-Day Cup game in May.
Verdict: Light on bowling but will compete for quarters
Last year: 4th, lost to Worcestershire in QF
Captain: Michael Klinger
Coach: Richard Dawson
Overseas players: Klinger, Andrew Tye
In a nutshell: The absence of Kiwi bludgeoner Kieran Noema-Barnett will be felt keenly, and Klinger's return as overseas appears to be driven by sentiment, given his struggles in the BBL where he averaged 14.50 and struck at 85.79 before retiring from the tournament. But don't write off a team boasting the all-round talent of Benny Howell and Ryan Higgins, or the top-order biffing of Miles Hammond; Hammond's hitting is unlikely to provoke lyrical description, but his pinch-hitting is vital to their gameplan.
Star: Only five times has a batsman scored at a quicker strike-rate in a T20 tournament than Jack Taylor did in the Blast last season (199.19), and the identity of those - Colin de Grandhomme, Andre Russell (twice), Alex Hales, and Lewis Gregory - demonstrates how impressive his year was. The only question is whether he can repeat the trick when teams are more switched on about his threat.
One to watch: David Payne has been doing his thing for years, finding any possible movement with the new ball and sliding the ball across right-handers, but flies under the radar due to a lack of pace. He ended last year as Gloucestershire's leading wicket-taker, and is the man they rely on for a good start; 12 of his 18 victims were top-order players.
Verdict: Weaker than last year; group stage exit likely
Last year: 8th
Captain: James Vince
Coach: Adi Birrell
Overseas players: Chris Morris
In a nutshell: A desperate season last year, with the dominance of 2010-15 a distant memory as they finished with two wins and nine losses. James Vince's availability - and the extent to which a poor World Cup has harmed his confidence - is important, but in Liam Dawson and Mason Crane they have a spin attack that could lead them to prepare the spinning Ageas Bowl wickets of old. Aneurin Donald has thrashed Championship attacks around in the past fortnight - keep an eye on his progress.
Star: Dawson was unused in the World Cup and might well feel short of match practice, but is a criminally underrated T20 player. 289 runs and an economy rate of 7.12 saw him emerge from last year with some credit, while Comilla Victorians and Peshawar Zalmi both benefitted from some tight spells and his ability to smack fast bowling over the winter.
One to watch: Rilee Rossouw is a madcap maverick, who chose the week of Hampshire's County Championship opener this season to tell the Daily Echo he expected to retire from red-ball cricket this year. He has struck at 84.40 in the Championship this season, and rarely gets out of T20-mode, so this should be a welcome return to the format. The leading run-scorer in the Bangladesh Premier League this year, Rossouw will bat in the top four and needs a better return than last year's 217 runs to prove he is worth keeping on a white-ball deal.
Verdict: Things can only get better
Last year: 2nd, lost to Lancashire in QF
Captain: Joe Denly
Coach: Matt Walker
Overseas players: Adam Milne, Mohammad Nabi
In a nutshell: Sam Billings' injury rules him out for the first half of the tournament at least, but Kent are a dangerous side. They missed out on Finals Day last year due to a quarter-final pitch that suited their opponents to a tee after a brilliant group stage, and recruitment has been excellent. Milne returns after a brilliant tournament last year, while Nabi's slugging and useful offspin are complemented by Hardus Viljoen on a T20-only, Kolpak deal. Joe Denly could play every game or none at all depending on Ashes selection, but they have the firepower to cope without.
Star: Milne missed out on New Zealand's World Cup squad due to injury, but is a quality operator at the death, and had the best Smart Economy Rate in the competition last season. He forms half of a hostile death-bowling partnership with Mitchell Claydon; teams might try to attack the middle overs in the knowledge that Kent's finishers are so frugal.
One to watch: Alex Blake's career average - a shade above 20 - demonstrates the futility of traditional statistics when it comes to T20 specialists. Ever since Blake burgled a win for Kent with a 30-ball 71* from number seven in 2015, teams have known that a game isn't dead until he is out, and despite hardly batting last year he remains an exceptional death hitter.
Verdict: Dark horses
Last year: 9th
Captain: Dawid Malan
Coach: Stuart Law
Overseas players: AB de Villiers, Mujeeb Ur Rahman
In a nutshell: Abject in 2018, with 12 defeats in 14 games rooting Middlesex to the bottom of the table. A potential top four of Paul Stirling, Dawid Malan, AB de Villiers and Eoin Morgan looks mouth-watering, though quite how often all four will be available together remains to be seen. They look light on bowling as usual, though Mujeeb is a good addition after an impressive World Cup. Have made the knockouts only once since their win in 2008; if Stuart Law can drag them to the quarters, it will be a minor miracle.
Star: Who else? De Villiers is only available for six games, but is sure to command attention, not least after the debacle of his non-inclusion in South Africa's World Cup squad and his subsequent denial of a U-turn. His six appearances will include a London derby at The Oval, and two outground appearances, at Cheltenham and Richmond; both will look comically small if he can get going.
One to watch: The club's hierarchy have put a great deal of faith in Nathan Sowter, the spiky Australian legspinner, having sent stalwart Ollie Rayner out on loan in order to give him Championship game time. Last year he only returned three expensive wickets, but managed 14 at an economy below 8 in 2017; if Malan trusts him to attack in the middle overs, he could be a star.
Verdict: Perennial strugglers and unlikely to break the cycle
Last year: 1st, lost to Sussex in SF
Captain: Lewis Gregory
Coach: Jason Kerr
Overseas players: Jerome Taylor, Babar Azam
In a nutshell: Ultra-aggressive last year, making it their own personal mission to disprove the aphorism that you can't lose three early wickets and still win, but consistently playing five bowlers cost them in the semi. Their gameplan will change this year, with Babar Azam providing the glue at the top of the order, and with no Corey Anderson the burden on Gregory as a finisher will be even higher. With a Championship title race on the cards and the One Day Cup in the bag, can they challenge on three fronts?
Star: Skipper Gregory had a stunning season last year, boshing 328 runs at a strike-rate above 200. His bowling has typically proved expensive in this format, but he is now free from the back pains that plagued him in previous years. As a captain, he is a Claudio Ranieri-style tinkerman - last year, one-over spells were par for the course - and in Jamie Overton, Max Waller and Tom Abell, he has three of the best fielders in the competition at his disposal.
One to watch: Tom Banton is now the worst-kept secret in county cricket, but has received fewer column inches than he might due to the inevitable focus on the World Cup. In the Blast, he has his chance to make a real imprint on the summer, and will have no fear in playing his range of ramps, paddles, and reverses, which complement his elegant hitting down the ground. Not many batsmen have IPL scouts circling when they are 20 and have four career T20s to their name; Banton could be the star of the tournament.
Verdict: Hard to picture them missing out on quarters
Last year: 5th
Captain: Jade Dernbach
Coach: Michael di Venuto
Overseas players: Aaron Finch, Imran Tahir
In a nutshell: Too reliant on Finch last year, whose runs couldn't quite drag them through the group stage. But an all-star bowling attack featuring Tahir, Tom Curran and Liam Plunkett should keep scores down, and all eyes are on Will Jacks after his pre-season hitting. The Ashes could prove tricky, though, with Rory Burns, Jason Roy, Sam Curran, and Ben Foakes all in contention to play for England; their depth will be tested as the summer rolls on.
Star: Has a single batsman ever dominated a T20 season in the way Finch did last year? In his nine innings for Surrey he managed 589 runs, with a strike-rate of 182.35 and a superhuman average of 147.25. Surrey won seven out of the nine games he played, and went winless in their five without him. Despite missing so much of the competition, he still scored 30 per cent of the club's runs; clearly, they will rely heavily on him again.
One to watch: Jordan Clark has made limited impact since his move from Lancashire, but T20 is where he thrives. His numbers suggest a talent wasted, with a career average of 22.47 and an economy rate approaching nine, but his opportunities with the bat have often been limited by a strong Lancashire batting lineup; can he realise his obvious potential as Surrey's finisher?
Verdict: Strong when everyone's there; Ashes a problem
Last year: 3rd, lost to Worcestershire in final
Captain: Luke Wright
Coach: Jason Gillespie
Overseas players: Alex Carey, Rashid Khan
In a nutshell: Laid claim to the best-ever T20 attack last year, with Rashid Khan, Jofra Archer, Tymal Mills and Chris Jordan the stars, and Danny Briggs flying under the radar, but fell short on Finals Day. This year they look even stronger: Alex Carey replaces Tom Bruce, who had a nightmare 2018, while Reece Topley adds to the fast-bowling stocks, and Stiaan van Zyl is fit again. On a nightmare run in the Championship, but it suits their lineup to free the shackles.
Star: Rashid Khan's availability has been confirmed for the first 10 games of the group stage, having sorted out his commitments to other T20 leagues. The world's best T20 spinner, he had a brilliant Blast last year. His World Cup displays fell well below his usual standards, but he is now Afghanistan's all-formats captain and will be Sussex's main man again.
One to watch: Delray Rawlins sent jaws to the floor last year with a string of clutch performances after coming into the side halfway through the tournament and his technically-perfect strokemaking, and is on a good run in the Championship. Look out for an early, nerve-settling boundary before he really gets going, and his left-arm spin that could be Sussex's sixth bowling option.
Verdict: Seriously strong - group winners