The ECB's new city-based competition is set to be a 100-balls-a-side affair, according to a radical proposal released today.
The concept proposes two eight-team competitions - for men's and women's teams - consisting of 15 traditional six-ball overs, and a final 10-ball over, a 20-delivery shortfall on traditional T20 matches.
The proposed approach was presented by the ECB to the chairmen and chief executives of the first-class counties and MCC on Thursday, and has been unanimously supported by the board of the new competition.
The ECB have also confirmed that Southampton, Birmingham, Leeds, London, Manchester, Cardiff and Nottingham will be the host cities for the five-week competition, with Lord's and The Oval each playing host to a London-based team.
"This is a fresh and exciting idea which will appeal to a younger audience and attract new fans to the game," said Tom Harrison, the ECB's chief executive. "Throughout its development, we have shown leadership, provided challenge and followed a process. We will continue to do that as the concept evolves.
"Our game has a history of innovation and we have a duty to look for future growth for the health and sustainability of the whole game.
"There are 18 first-class counties, playing red and white ball cricket, at our core and these counties and competitions will be supported, promoted and benefit from the game's growth."
The radical proposals are an attempt to differentiate the ECB's tournament from the T20 franchise competitions that have already taken root globally - including the IPL in India, Australia's Big Bash, and the Caribbean Premier League - as well as the existing Vitality Blast competition, featuring all 18 counties, which will continue concurrently.
The loss of 20 balls per innings will help to ensure that the competition fits comfortably into a three-hour window, with all matches expected to finish by 9pm.
However, the proposed 10-ball final over may require buy-in from MCC's law-makers, seeing as Law 17.1 currently states: "The ball shall be bowled from each end alternately in overs of 6 balls."
Sanjay Patel, the ECB's chief commercial officer, and MD for the new competition, said: "The development team has had strong support and encouragement in its conversations to date and it's time to take the concept wider as we build the detail.
"This is 100-ball cricket, a simple approach to reach a new generation. Based on 15 traditional six-ball overs, the other ten balls will add a fresh tactical dimension.
"Crucially, this will also help differentiate this competition from Vitality Blast and other T20 competitions worldwide, maintaining our game's history of successful innovation.
"The players and our valuable broadcast partners under the new TV partnerships from 2020-24 are vital to the success of this competition and they will see the energy, excitement and simplicity of this approach."
The five-week competition will feature both men's and women's team in concurrent competitions, as the ECB seek to build on the explosion of interest in women's cricket since the World Cup win in 2017.
"Our World Cup win at Lord's last July showed what's possible in terms of our sport reaching a new, younger and more diverse audience," said Clare Connor, the ECB's Director of Women's Cricket.
"Kia Super League has had a huge impact on participation, player development and the profile of our game. It was a big investment and a bold decision by the Board and paved the way for this next stage of growth.
"To build the women's and men's competitions and identities together, side by side, is a prospect that few sports ever have and will give us greater reach, scale and prominence.
"It will attract more women and girls to the game, ensure that cricket reaches and entertains more families and give our players an exciting stage upon which to display their talent."
The proposals represent the biggest shake-up to English cricket since the launch of the original Twenty20 Cup in 2003.