Product Description This casement operator features a 9 in. long steel constructed arm driven by a worm gear mechanism. It mounts to the left side of your window when viewed from the inside. It has a 5/16 in. spindle and mounts on 3-7/8 in or 4-3/4 in. hole spacingft.s. Used o From the Manufacturer This casement operator features a 9 in. long steel constructed arm driven by a worm gear mechanism. It mounts to the left side of your window when viewed from the inside. It has a 5/16 in. spindle and mounts on 3-7/8 in or 4-3/4 in. hole spacing's. Used o