Back ground info- Bought a 2001 KX 125 with a known front brake issue- Guy said it probably just needed a rebuild kit and it would be good to go- He had some aftermarket levers and had drilled a hole in the flange that contacts the piston to allow for a bolt to go through- the stem was so long that it was hitting the throttle casing. Anyways-- Tossed the old stuff- got new levers and ordered a kit. And the trouble starts- I got online and ordered an All Balls rebuild kit and it wasn't the right size-- Got online and ordered yet another kit, this one for a 2001 - 2005 KX 125 from RJATV that came with a new piston, seals, clip, spring and washer- again too big to slide into the master cylinder- The Master cylinder is a Nissin and rather than the standard 11 that is stamped near the banjo bolt, mine reads 3/8 I measured the pistons of the rebuild kits and they were 11 mm.....the one that came with the bike measured 9.5mm I am completely at a loss on what kit to order as this master cylinder is clearly not the original nor is it the standard nissin 11mm that most KX/RM/CR/YZ 125-250 use. I have googled until my finger tips bled and have found nothing- I have scoured ebay in search of master cylinder pictures in hopes I would spot one that has 3/8 stamped on it- No luck. It has been difficult to say the least as I can't even go to Bikebandit or Rocky mountain ATV and order OEM because it will be the 11mm piston - The easiest thing was to just find a good used 11mm master cylinder and be done with it ( I am just not sure if I will have to buy a new brake line and caliper) but the curiousity is killing me- Does anyone have a suggestion of what bike used a 3/8 nissin master cylinder? Any help would be great!