I install excedium racing differential collars on my ap2 2005 s2000. It is a perfect fit product, a real big improvement, more drivetrain precision. The biggest problem is that it come without instruction and no info is avaliable for it. Not a big issue except that we dont know if we need or not reinstall the oem washer between the bolt and collars like the evs racing that come with instruction and specify that you dont replace this washer (remember that is a totally different design, really not the same and totally out of price vs exceduim collars). For me, i try with washer, without it and with a 1/2 thin oem washer and finally, i replace the oem washer and it seem to be good after 3000 miles hard running time (without the washer, its more smooth but the oem nut seem that it will pass trought the collar hole!!