The resistor unit (10) comprises resistors (12,14,16) connected to electrical terminals (24,26,28,30,32) secured to an insulating plate to which first and second legs (64,66) of a spring sheet metal mounting clip (60) are secured for insertion through an opening in a supporting wall. The legs (64,66) are bent forwardly from a rear member and are formed with first and second spring latching members including ramp portions bent laterally from the legs (64,66), shoulder portions bent inwardly from the ramp portions for wedging engagement with edge portions of the wall, and front end portions bent forwardly from the inner ends of the shoulder portions. A soft resilient expanded rubber gasket is mounted on the plate for sealing engagement with a rib projecting forwardly from the wall around the opening. The spring force produced by compression of the gasket is counterbalanced by the wedging action of the shoulder portions, so that rattling is prevented. The legs (64,66) are inserted with an interference fit into opposite end portions of the opening. The rear clip member and the opening have similar nonsymmetrical shapes affording unique orientation of the resistor unit (10). The clip (60) also protects the resistors from damage during shipment.