T20 best: Winners 2014, Beaten finalists 2003 and 2017. Semi-finalists 2015.
2017: BF; Run Rate 8.76; Economy Rate 8.53
Captain: Grant Elliott
Coach: Jim Troughton
Overseas Players: Jeetan Patel (NZ), Colin de Grandhomme (NZ)
Ashley Giles, director of cricket at Edgbaston, assembled a new-look T20 side so successfully in his first season in charge that the Bears finished beaten finalists, outdone by Nottinghamshire on their home turf. Colin de Grandhomme arrived to little acclaim but hit the ball far and often and Ed Pollock's emergence was important. Jeetan Patel - 20 wickets at an economy of 6.82 last season - is a vital cog and if Josh Poysden's legspin comes good the Bears will have even better balance. Can Ian Bell get a gig in the middle order alongside the stylish Sam Hain?
One to watch: Henry Brookes' call-up for the Lions squad for the triangular against India A and West Indies A confirmed him as among the most exciting teenaged quick bowler in the country. Strong, willing and able.
In a word: Consistent
T20 best: QFs in 2017
2017: QFs; RR 8.74; ER 8.82
Captain: Gary Wilson
Coach: John Wright
Overseas Players: Wahab Riaz (Pak), Lockie Feguson (NZ)
Derbyshire's poor Championship season was spruced up last summer by their first T20 quarter-final appearance. Calum MacLeod, who shot to prominence with a century to beat England in an ODI in Edinburgh (the same England who went on to beat Australia 5-0) has become an exciting acquisition. But Luis Reece, who struck 14 sixes last season, will miss a large chunk of the Blast with a broken foot. Wahab Riaz, omitted from Pakistan's tour of England, will be eager to prove a point and he was the leading wicket-taker in the PSL with 18 victims at an economy of 6.90.
One to watch: Matt Critchley, a 21-year-old allrounder from Wigan, made a blistering 64 from 37 balls for the North against the South in Barbados earlier this year and he could do well with bat and ball.
In a word: Underrated
T20 best: BF 2016
2017: 9th, North Group; RR 8.00; ER 8.96
Captain: Tom Latham
Coach: Jon Lewis
Overseas Players: Tom Latham (NZ), Imran Tahir (SA)
Durham had the lowest strike rate in North Group, at only 133 runs per 100 balls, in 2017 and even though they can use their geographical location as the most northerly county as a partial excuse, their absence of power hitters left them bottom of the table. Paul Collingwood can only mask so many deficiencies. The last-minute signing of Imran Tahir has at least completed their overseas stocks, but it is hard to escape pessimism about the season that awaits. At least attendance figures should be boosted by big discounts allied to the All Stars development scheme.
One to watch: South African allrounder Gareth Harte showed promise in the Royal London Cup with lower-order runs then added a maiden Championship hundred to help turn the game against Leicestershire - he should gain further opportunities in the short format.
In a word: Bereft
T20 best: Winners 2015: BF 2005, 2014.
2017: 7th, North Group; RR 8.44; ER 8.22
Captain: Liam Livingstone
Coach: Glen Chapple
Overseas Players: Joe Mennie (Aus), James Faulkner (Aus)
James Faulkner's T20 reputation has dipped a little in these days of detailed statistical analysis but Lancashire have kept faith with the Australian allrounder, who was part of their 2015 winning side. New skipper Liam Livingstone has the capacity to be a star of the tournament, despite a dismal record of two fifties in 42 T20 appearances, but Lancashire disappointed last season and their Championship form has left them near the foot of Division One. Jos Buttler might sneak three matches at the end of July - including a Roses match. Much is needed from allrounder Jordan Clark
One to watch: Legspinner Matt Parkinson is a rising star. He entered the T20 midway through last season and took 14 wickets from nine matches with an outstanding economy rate of 6.06. Parkinson took 18 wickets in the most recent Royal London One-Day Cup, and even bowled at the death.
In a word: Dangerous
T20 best: Winners 2004, 2006, 2011
2017: QF, North Group; RR 8.10; ER 8.38
Captain: Colin Ackermann
Coach: Paul Nixon
Overseas Players: Mohammad Abbas (Pak), Mohammad Nabi (Afg)
Talk of Leicestershire as English cricket's most successful T20 county sounds outdated, but they reached the quarter-finals last summer and ambitions have been sharpened by the arrival of Paul Nixon as county coach. Leicestershire's overseas recruitment looks exciting with Mohammad Abbas, skilled in English conditions, joined by the wily Mohammad Nabi, one of three Afghans in the Blast, who Nixon expects will bring control with the ball and nous with the bat. Cameron Delport, a heavy-hitting South African much sought in T20 leagues, smashed 109 from 59 balls against Nottinghamshire to help the Foxes qualify for the last eight in 2017.
One to watch: Callum Parkinson, twin of Lancashire's leg-spinning Matt, picked up 15 wickets with an economy rate of eight last season, and often bowled in the Powerplay. A unsung but important component of the Foxes' attack.
In a word: Improving
T20 best: Winners 2013, 2016; BF 2015.
2017: 6th, North Group; RR 8.61; ER 8.97
Captain: Alex Wakely
Coach: David Ripley
Overseas Players: Seekugge Prasanna (SL), Rory Kleinveldt (SA)
Northants' T20 love affair faltered last season and their economy rate of 8.97 was one of the worst in North Group. That makes Richard Gleeson's form with the ball a crucial factor. Gleeson missed the 50-over competition with an elbow problem and Northants will need his excellent yorkers. There is no Azharullah at the death after his retirement, but Brett Hutton has been a good all-round signing. They will again look for runs to the burly South African Richard Levi, who piled up 375 runs in eight innings at a strike-rate of 167.
One to watch: Ben Duckett made a dreadful start to the Championship season, as if the brouhaha that surrounded his high-jinks in a Perth bar during England's Ashes tour was still hanging over him. But signs of form, notably a quick hundred in Cardiff, will encourage Northants that his talent could flood out during the Blast. It will be a long route back to England, but he has the ability to be a star of the Blast.
In a word: Unpredictable
T20 best: Winners 2017; BF 2005.
2017: Winners; RR 9.60; ER 9.10
Captain: Dan Christian
Coach: Peter Moores
Overseas Players: Dan Christian (Aus), Ish Sodhi (NZ)
If Outlaws captain Dan Christian lifts the trophy again this summer he will probably be required to read an ECB Health & Safety pamphlet before he does so - last September he managed to draw blood by cutting his eyebrow. Christian is back at Notts for a fourth season and in that time Trent Bridge has favoured the batsmen as much as any in the land, courtesy of placid pitches and short boundaries square of the wicket. Alex Hales, Riki Wessels and Samit Patel take some stopping here. Ish Sodhi is Notts' choice from the legspin fraternity, but Paul Coughlin is still recovering from a dislocated shoulder and is a sad loss. Notts have reached the knockout stages nine times and can extend that record.
One to watch: Tom Moores came into the side last season and this summer has also offset the Championship retirement of Chris Read, a Notts legend, in exemplary fashion. Even David de Gea, Manchester United's goalkeeper, has remarked upon his athleticism. Joins Ben Foakes, Ollie Pope, Alex Davies and Ben Cox in a host of exciting young batsman-keepers in county cricket.
In a word: Gluttonous
T20 best: QF 2004, 2007, 2012, 2014, 2015
2017: 8th, North Group; RR 8.36; ER 8.95
Captain: Moeen Ali
Coach: Kevin Sharp
Overseas Players: Martin Guptill (NZ), Travis Head (Aus), Callum Ferguson (Aus)
Worcestershire's batting looks destructive, but question marks over their bowling make it difficult to fancy them for a last-eight spot. Overseas batsmen are permed from Martin Guptill, Travis Head, who captained the Adelaide Strikers to the Big Bash title this year, and his fellow Australian Callum Ferguson, who hit the county's highest List A score of 192 in the One-Day Cup. Add that to the sheer quality of Joe Clarke, verve of Brett D'Oliveira and mighty leg-side hitting of Ross Whiteley, whose six in an an over last season (the first Englishman to achieve it) earned him T20 opportunities in Pakistan and Bangladesh.
One to watch: Ed Barnard is a fast-improving allrounder who relishes the climax of a game whether with bat or ball. He will take on heavy responsibility given the absence through injury of Joe Leach and Josh Tongue and with the Rapids using their overseas contingent, somewhat contentiously, to bolster their batting strength.
In a word: Exposed
T20 best: BF 2012
2017: 5th, North Group; RR 9.64; ER 8.82
Captain: Steve Patterson
Coach: Andrew Gale
Overseas Players: Kane Williamson (NZ)
An underlying sense of grievance has followed Yorkshire all season. Not only do they have to survive a heavy supply of players to England and the Lions, but Liam Plunkett and David Willey were pilfered as IPL replacements, New Zealand clipped Kane Williamson's involvement from 11 matches to nine and Cricket Australia changed their mind about Billy Stanlake's deal. "We'll manage with what we've got" was Yorkshire's understandably impatient conclusion, even though England ODI calls are inevitable. Yorkshire's stats suggest not to qualify for the quarter-finals last season was an aberration and they must rid themselves of careless losses on the road to put that right.
One to watch: Yorkshire will look to the bony veteran Steven Patterson, thrown into the captaincy at 33 after Gary Ballance stood down, to manage a high-quality squad that nevertheless, without Stanlake, looks one piece short of the jigsaw. His first task is to draw a career-best season out of the highly-promising Matthew Fisher; his second to ensure legspinner Adil Rashid is reintegrated happily - Rashid's insistence on a white-ball only deal added to Yorkshire's vexation, but they will need him relaxed and in form.
In a word: Restless