Unrivaled Low Signature Device Black LSD-5.56 UMMS HUB 1/2-28. LSD front is printed from 17-4 stainless and post machined to tight tolerances. This is because many of the features of the LSD can not be machined. It is attached to the UMMS HUB or SLK rear which are machined from hardened 4140 steel. Specifications for Unrivaled Low Signature Device: Manufacturer: Unrivaled Color: Black Caliber: 5.56mm Threads per Inch: 1/2x28 Package Contents: Unrivaled Low Signature Device Unrivaled (LSD-5.56 UMMS HUB 1/2-28): Low Signature Device Black