Yes they are diffrent! I brough the dt125r 99 ypvs from a lad that had just put in a new jesil race crank in and sold it to me as just needs new head gasket, so popped one in and bang it went! i then groved a ring around the bore of the head and poped a Heat rated orange o ring in with this heat rated glue stuff! It worked i then put and standard exhaust in down jetted from 240 to 210, not long after it blows up 4 miles from home 2300 long walk home, so i brough a copper gasket same again. 2 base gaskets (lowers the compression) ive read on here? Same as then saw this and checked mine 3mb00 barrell and 3mb head, looked on ebay to see if yama sold a 3mb head and it is very diffrent! like is Has got an little adge around the bore giving better hold of the compression than a 3bn that is complely flat, my question is can i still use my copper gasket or go for the standard one what also has the imprint of the little adge around the bore? And a thank you i wouldnt have figured it out without this page!!!