Introduction In the year of 2015 we designed and developed the RM27, RM30, AM35 and AM40 series of carbon fiber mountain rims. These four mountain rims incorporate aerodynamic design concepts, which are beautiful in appearance and extremely strong. Based on the design shape of AM40 series, we developed a DH series mountain rim with an unprecedented rim lip thickness of 4.5mm in size 26", 27.5" and 29". The weight of model NXT27DH40 is 570g. The profile drawing of this rim is as below. This rim could be used for Trail, Enduro, Freeride and Down Hill riding. The tire size for this model of rim is recommended at 2.1" ~ 2.85". The tire pressure is recommended at 30 ~ 60 psi.