Marvin Classic Old Style Case-Master Casement Windows, Marvin Clad and All Wood Models - Dimension of "B" Lengths or Short Arms May Vary from 4 7/16", 2 7/8" or 3 3/4" CASEMASTER, MARVIN AWNING and Marvin FRENCH CASEMASTER units. Operator Replacement Stampings may be RF-15, 20810, 30744, 20811, 30841, 30842, 30741, 30742, 31538, 31539, 30472, 30470, P234DC P233DC and others.  

Specify Handing and "B" Arm Length in the Comment Section at Checkout.

If None Specified, We Ship "Left Handing" 4 7/16" "B" Arm