The Shure RPW112 Wireless SM58 Cartridge Housing Assembly and Matte Grill.

Cartridge Replacement Microphone Head Assemblies for Hand-held Wireless Transmitters
To replace a cartridge assembly, proceed as follows:  

1. Using the supplied .035 in. (0.9 mm) hexagonal-head wrench, loosen the setscrew in the handle of the microphone-transmitter. No setscrew is present on the T2, LX2, SC2, U2, ULX2, SLX2, UC2, UT2, PGX2 and UR2 microphone-transmitters.

2. While holding the microphone-transmitter with the grille pointing upward, unscrew the grille and cartridge by turning them counterclockwise, and remove them. The wiper contact design requires no further disconnection.

3. Screw the replacement cartridge onto the handle and tighten it.

4. If you are using an L Series or EC Series transmitter, tighten the setscrew on the transmitter.