There is the Old School Street Twin "Original" that uses a B&B design pressure plate. That thing is a monster, good to over 1200hp or something like that.

McLeod had developed a softer version of that. Still a twin clutch, but smaller diameter, can use stock flywheel, and is a diaphram pressure plate with a super low 1800lbs!...compared to a Centerforce DF of around 3400lbs. These are the RST and RXT street twins. RST is all organic disc and good to 800hp and the RXT has dual friction material and is good to 1000hp. Both are diaphram and super low pedal pressure. They are supposed to hold like mad, but super nice engagement,....very smooth!!!! I hope my RST doesn't break stuff.