ASTM/SEI The ASTM (American Society for Testing and Materials) is an organization comprised of thousands of skilled volunteers including doctors, engineers and physicists. It is the job of the ASTM to set standards for many types of safety equipment. The ASTM has created criteria for horseback riding helmets to adhere to. These standards are summarized in ASTM F 1163. The SEI (Safety Equipment Institute) is an independent laboratory that tests helmets to be sure they meet the ASTM standard.