Darren Till will face the toughest test of his Bare Knuckle Fighting Championship career when he faces Yoel Romero.
The two former UFC fighters have removed the gloves to embark on adventures in a wholly different combat sport.
Here's everything that UK fans need to know about the BKFC94 event...
When is Darren Till vs. Yoel Romero?
Darren Till and Yoel Romero will fight on Saturday, Sept. 26 at BKFC94. It goes down at the AO Arena in Manchester.
How to watch Darren Till vs. Yoel Romero in the UK
Till and Romero's fight is being broadcast by DAZN on pay-per-view.
Start time for Darren Till vs. Yoel Romero
The fight is in the UK so fans can expect the main-event before midnight on Sept. 26. The event begins at 7 p.m. BST.
What is at stake?
The UFC careers of Till and Romero are over. Both fighters were world title challengers and, even though MMA is now behind them, they have revitalised their careers thanks to the Bare Knuckle Fighting Championship.
Till and Romero never fought in the UFC -- the Liverpool fighter would often joke that he was keen to fight any challenger except for the fearsome Romero.
But, Romero is now 49 and Till is still just 33. Clearly, youth favours the Brit.
Cuba's ex-Olympian Romero has a 1-1 record in bare knuckle boxing and, earlier this year, won his only bare knuckle MMA fight.
Till, meanwhile, won his BKFC debut against ex-reality TV star Aaron Chalmers. Previously he beat Luke Rockhold under boxing rules.
What Till still has in the tank remains to be seen. His fight against Romero gives him an opportunity to claim arguably the best win of his career in any discipline. It also has the potential to set up further big nights for Till in BKFC or beyond.
Weight class
Till and Romero are meeting at cruiserweight (205 pounds). The champion is Esteban Rodriguez who has a 7-1 record.
What are bare knuckle boxing rules?
The fighters don't wear gloves, obviously, but can wrap and tape the wrist, thumb and mid-hand. The fights are five two-minute rounds.
Only a punch with a closed fist is legal. Clinches can be broken up by the referee after three seconds. Fighters can use their spare hand to punch out of the clinch.
Knock-downs are the same as traditional boxing. A fighter has 10 seconds to stand up if they are knocked down. Fighters cannot punch a downed opponent.
The doctor can be called in if a fighter cannot see due to blood. They have 30 seconds to stem the wound. But if blood continues to stop a fighter from seeing, the referee can award victory to his opponent.
BKFC uses a circular 'ring' with four ropes.
Undercard
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Gaz Corran vs. Mac Bygraves
Karl Thompson vs. Andy Thornton
Joe Lister vs. Harry Bray
Mikey Henderson vs. Matthew Wiwczaryk
Stew Martin vs. Curtis Davies
Ste Wallwork vs. Leigh Cohoon
Luke Vaughan vs. Bartlomiej Krol
Liam Dooley vs. Tyrone Hamer
Benjamin Lowe vs. Dan McGraffin
Luke Bassnet vs. Darren Willans