Pemkoprene, PK33 supplied in black finish, 20 foot piece. Excellent resistance to compression set, particularly at elevated temperatures and for extended periods of time. Stays flexible between -40 degrees (F) and 250 degrees (F) with very high resistance to flex fatigue. Smoke tested in accordance with UL1784-01; meets the requirements of NFPA 105 "Standard for the Installation of Smoke Door Assemblies and Other Opening Protectives".