Metal / Steel Construction Compatible with all 20mm weaver and Picatinny accessory rails Equipped with locking retention thumb nut for a secure accessory Enhances shooting accuracy with accessible wind and elevation adjustments QD system for easy mounting and adjusting for personalization and comfort to rifle set up In the Box 1X M4 / M16 Rear Sight Specifications: Build Full Metal / Steel Compatibility Fits all 20mm / Picatinny / Weaver Rails Color BLACK California Proposition 65 Warning: Cancer and Reproductive Harm - www.P65Warnings.ca.gov