If your Truth window operator is stamped with any of these number 20544, 30636 or 30637, then you probably have the Truth Entrygard Dyad Operator 15.11. We find the numbers 30636 or 30637 on the “S” shaped arms, and the 20544 stamped on the linkage arm, the one with the stainless steel clip. This linkage arm offsets down. The “S” shaped are is no longer available, and has been replaced by a diamond shaped connecting arm. The old style “S” shaped arm was twisting when the window was sticking. The biggest problem we see with this operator is the worm gear pulling out of the housing. This causes the operator and work in one direction, but not the other. If you window is working in one direction, but not the other, or if your handle is coming out of the operator, then the only solution is to replace the operator. Below I show a new style 15.11, and an old style 15.11. We keep these in stock and can be ordered on our website!