The version with the 11″ arm is no longer manufactured. If yours measures 11″, replace it with the 9 1/2″ version.
To determine arm length, measure from the center of the gear box to the center of the roller on arm.
To determine left or right handing, view window from outside. If hinged on the left, order a left hand operator.
For units such as Norco, D series, Jeld-Wen JEL-N-330 , Malta, Caradco, Alenco, Norco, Pozzi, Rockwell, Vedder, Wenco and others.