39-187 with 4.5" link arm

A home owner from MA says:
I ordered parts for my window and think I may have the wrong size. I found your parts via this discussion.

The person submitting it had identical part as mine. Your company suggested parts #39-187 and 39-188. The arms on mine are 4.5 inches (as in the pictures from the link). The ones's I received are 5 inches.

Do you carry them in 4.5 inches or are they interchangeable? I tried to install but the window didnt seem to want to close all the way.

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Tom from SWISCO responded:
Hmm... do you think you have the 39-089 and 39-090 instead? The link arm for these is also 5" but the gear arm is different and may compensate for that 1/2".

You see, the 39-089 and 39-090 have a gear arm that's shaped more like a Z, while the 39-187 and 39-188 has a gear arm shaped more like a W. The difference is subtle, and hard to spot at first, but if you look closely you can see what I mean.
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