DT Swiss XM 421 Rim - 27.5" Disc Black 32HDT Swiss XM 421 Rim 27. 5" Disc Black 32H. The XM 421 is as good as an All Mountain rim can get yet still fears no trail no matter what rock gardens it has on the menu. Tubeless Ready Alloy rim (tape valves and sealant sold separately) 2. 0 silver alloy Prolock Squorx Pro Head nipples and PHR washers included The wheel must be built with the supplied PHR washers and Pro Head nipples. The PHR washer must be positioned between the nipple and rim and fit