no part numbers anywhere

I cannot find any part numbers on any part of the window, balance system, or any of these tiny plastic parts. The only thing I have are these pictures....they keep breaking off of my windows, the house was build in 1988. Its 15/16in long, 5/8in wide, and 1/2in deep. It looks like part "Product Code: 18-066"...but without one of the holes in it

Hi Paul, Thank you for looking into that for me! I bought 4 of them a couple days ago from you guys. When they arrive I will see if they fit...I figure worst case is that I have to customize them a little bit to get them to fit. I will update. Thanks!

Hi Paul, I have another question for you. The parts arrived today, and unfortunately they did not all fit on my windows. I had one fit, and I can see the problem with the others. In the picture of the window below, there is a black strip of plastic or hardened rubber that runs all the way to the top of the window. If I cut that plastic below the height of the sash guide, the sash guide will fit. Do you happen to know what that piece of plastic/rubber is called that runs inside the window? One of my windows had part of this black piece missing at the top, so the sash guide fit perfectly and is doing the job. If i cut out the top inch of this black piece on the other windows, the sash guide will fit.

I am also curious, will new channel balances help make the windows smoother/easier to open? The windows are hard to open and close and it looks like the spring in the balance is rather rusted/old....I am not sure if these windows should require this much force to open or close, and if a new balance would help?

Thank you so much Paul, I appreciate your help more than I can express. I bought my first house Feb 2019 and it has been a lot of work and a lot of learning so far! I ordered two Series 351 for the appropriate window weight and balance length, and a few more of the 18-006 sash guides. It's looking promising! I'll be sure to leave a good review!