A quick learner from Weeki Wachee, FL 34607 says:
March 1, 2013
I think your part #18-044 top sash guide is the closest thing I can find to replace broken guides on my windows. Typically the little tab that catches on the spring breaks off. However the top of my guides is 7/8 by 182, not the 7/8 by 11/16 of your part. Can I use your 18-044 as a replacement on my windows?
Paul from SWISCO responded:
March 6, 2013
Thanks for posting! Have you seen our 18-166? Could that be a better match? Check it out and see what you think.