if the boxter calipers are anything like the 993 calipers, they will not fit under the 15" rim. some 16" may not even work. when i had todd c. put on 993 brakes on my CQ, my rims barely fit, and my bbs need spacers (both 16x7.5, et35). check first, then buy. -eric ferguson '90 CQ 20v, not so stock