Strut = Strut, insert = insert
the oem rear strut housing is longer than the oem front housing. the B15 yellow "insert" is about 1" shorter than the front oem strut housing and i think it was like 3" shorter than the rear. the front needs to be shorter to gain travel. the B13 rears are fine, no need to go 3" shorter unless you want to go coilovers, then it would be okay.