I don't remember the size off the top of my head, but if you still have the OEM tool kit, there should be a wrench in there that fits and is marked with the size so you'll know what socket you need to buy for a quality solution. Both Clymer & Haynes have manuals for thr B12, but I'll save comments on them for those that have experience with them. I just have the Suzuki one and it's been fine for my needs, but then I'm not new to wrenching on things.