Batsman Will Rhodes, fast bowlers Ryan Sidebottom and Henry Brookes, and all-rounder Alex Thomson sign new Warwickshire deals.
The England & Wales Cricket Board confirm their new competition in 2020 will be 100 balls a side - made up of ten 10-ball overs.
County champions Surrey will start their defence of the title in April 2019 with a home match against Essex.
Warwickshire and England batsman Ian Bell is signed by Pakistan Super League champions Islamabad United.
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Birmingham Bears captain Grant Elliott tells BBC WM's Bears Podblast he is to retire from professional cricket at the end of the season.
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How to get into cricket
How to get into cricket - physical exertion with a chess-like element in matches which range from half an hour to five days.