Surface mount. High pressure die-cast zinc case, handle and knob in a baked enamel finish; hardened steel arm, drive worm and gear are protected with corrosion-resistant finish; nylon roller assures smooth operation; operator provides a full 90 deg. window openings and disconnects easily from the sash; painted steel track. Contents: 1 operator, 1 handle, 1 track, and 1 set of installation screws. Model No. 173551 (SKU 258644) is right hand and model No. 173552 (SKU 258652) is left hand. Fits Truth hardware. Handing determined by window hinge position when facing window exterior.