Sunair window

Thanks for posting. I actually don't have any record of Sun-Air windows using the Series 371. There are other balances that look quite similar to this at first glance, so to be safe you might want to send detailed pictures of the balance, in particular the fittings at both ends. That would help confirm exactly what your working with. I'm also not entirely sure of the screw-on pieces in the frame you're referring to, so if you could send pictures of them as well, we will do our best to find what you're looking for. 

Thanks for posting. OK, I'm glad we checked. These balances are actually either the S380-34 or S385-34. The only difference between these two types of channel balances is the depth of the bottom nylon shoe, or the 'heel-to-toe' measurement. See the diagram below for reference. Compare both with your old hardware to see what matches best. In either case, for the stamp option select 3340. 

Comparison of the S380 and S385 balance shoes.

The other part you show is a Top Sash Guide. Specifically I think you need the 18-171. Take a look, compare the dimensions below to your old guide, and see if you concur.

Alternate image for 18-171

Alternate view of 18-171

Alternate view of 18-171

That's right! Just add the items your cart via their respective shop pages (don't forget to set the quantities you need!), then click "Checkout" in the top right corner of the screen. From there you'll be able to choose shipping options and pay for your items. Let me know if you have further questions!