Roto Interlock casement window operators are offered with a short arm that will also use a connecting arm, a 6" straight arm and a 10" straight arm length. Connecting arms for short arm Roto operators are 39-497, 39-791 and 39-817. Compatible crank handles: Traditional handle 37-157* and Folding handle 37-213*. (* denotes color). Roto Interlock sill mounted window operator replacements.