GrovTec US 48 Pack 0.875in Machine Screw w/Nut and Spacer Black. The standard swivel stud is made of steel and has an inner lining of felt so it doesn't scratch or damage your firearm. These GrovTec Machine Screws w/ Nut & Spacer include steel spacers for a more secure fit and the metric swivel studs are easy to install and detach. GrovTec Machine Screws w/ Nut & Spacer are precision machined from high quality steel with durable black oxide coating. Because of the unique patented locking nuts these GrovTec Machine Screws w/ Nut & Spacer will never require a re-zeroing even after numerous installation. Specifications for GrovTec US 12 Pack 0.875in Machine Screw w/Nut and Spacer: Manufacturer: GrovTec US Color: Black Fabric/Material: Steel Length: 0.875 in Package Contents: GrovTec US 12 Pack 0.875in Machine Screw w/Nut and Spacer GrovTec US GTHM54: 48 Pack 0.875in Machine Screw w/Nut and Spacer Black