SEE THE PIC BELOW FOR ALL THE DIMENSIONS THE HEADS WE SELL THAT WORK WITH THIS PISTON KIT ARE LISTED AT THE BOTTOM OF THIS PAGE, SCROLL DOWN PLEASE. THIS WORKS ON TRX90'S THAT HAVE "BIG_DOME" OR "OLD_70_DOME" HEADS HEADS FROM THE FOLLOWING WILL WORK GREAT: XR/CRF50/70 RACE HEADS WITH 22MM AND 25MM VALVES. CT70_K0_TO_1977 ATC70_ALL ALL_SL70 ALL_XL70 ALL_CL70 C70M_1970/71 54MM HI_COMPRESSION BIG_BORE CYLINDER_KIT TRX90_114CC 54-GBO/1-18/2-11 $109.99 CLICK ON PICTURE ONCE THEN AGAIN FOR DIMENSIONS CLICK ON PICTURE ONCE THEN AGAIN CLICK ON PICTURE ONCE THEN AGAIN CLICK ON PICTURE ONCE THEN AGAIN CLICK ON PICTURE ONCE THEN AGAIN CLICK ON PICTURE ONCE THEN AGAIN HEAD_DOME'S_? RODS_LONG/SHORT_? WHICH_DO_I_HAVE_? THESE ARE THE AREA'S TO BE TRIMMED FOR THE 54MM CYLINDER MUST REMOVE SOME ALUMINUM HERE FOR 54MM CYLINDER MAKE SURE TO SLIDE CYL. DOWN STUDS TO CHECK FOR CLEARANCE SLIDE BARE CYLINDER DOWN STUDS AND MAKE SURE ALL IS FLUSH