Casement operator 9 1/2" long arm about 4" short

This window operator is a match for either the 39-253RB or 39-439B Encore Dual Arm Operators. The dimensions for them can be found on the website. To determine which of these is the correct replacement, you'll need to review the attachments at the end of the arms. 

Please see the tutorial below for a detailed explanation on the differences between the two. 

The compatible hardware and accessories can be found in the related products before their product descriptions.