The Simplex hammer head housing only; without inserts or handle; with integrated handle-protection sleeve. Allows the custom-build of a Simplex mallet that suits your specific needs perfectly. Required hardware for assembly as bolt; nut and spring washer; is included. Cast Steel. This regular cast steel housing is a very good choice for most medium weight applications. It offers good noise dampening and vibration reduction. If you ever want to use copper insers; the reinforced housing is required. Diameter: 40mm. Weight: 420 gram.