For DOWNWARD OPENING FLAP DOOR used with piano, butt or drop hinges (SDH 001, SDH P, ). SDS C100 (with catch) is designed to hold door in closed positionSDS 100 does not have a catch feature. Designed to be used with a magnetic catch or touch latch. Non handed. Torque Calculation:Torque = Door Height 1/2 Door Weight Per Piece: 35~50 kgcm (30~43 lbsinch) Per Pair: 70~100 kgcm (60~86 lbsinch) Recommended Door Thickness: 20 mm (25/32") Short arm version SDS-100TV (or C100TV) for smaller door height availableWARNING: This product can expose you to acrylonitrile, butadiene, chromium, nickel, 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.