For DOWNWARD-OPENING FLAP DOOR used with piano, butt or drop hinges (SDH-001, SDH-P, P.238) When pushed to close, HDS-10S is designed to self close and soft close Used in pairsTorque Calculation: Torque = Door Height x 1/2 x Door Weight K-Type:60~95 kgf.cm(52~82 lbs. Inch)/ pair M-Type:95~130 kgf.cm(82~112 lbs. Inch)/ pair H-Type:110~160 kgf.cm(95~138 lbs. Inch)/ pair S-Type:140~180 kgf.cm(121~ 156 lbs. Inch)/ pairWARNING: This product can expose you to acrylonitrile, butadiene, styrene, which are known to the State of California to cause cancer and birth defects or other reproductive harm. For more information, go to www.P65WARNINGs.ca.gov.