A wearable device has a housing containing electronics and a band that retains the wearable device on a user's arm. Each end of the housing has an open receptacle. The band has protrusions made from an elastomeric material and includes a rigid member arranged at least partially within. The protrusions are inserted into the receptacle to attach the band to the housing. A lower portion of the housing comprises two pieces that, when assembled, provide optical baffles between adjacent optical devices such as a heart rate monitor, and windows for the optical devices to operate. A thermal conductor is retained between the two pieces and facilitates operation of a temperature sensor in the device. An antenna carrier facilitates installation of an antenna without impairing fixation of an upper portion of the housing. A compact charger clips to the housing to supply power to recharge a battery in the wearable device.