Window parts need to be identified.

Thanks for contacting SWISCO. I can't be 100% sure without seeing the Top Sash removed from the window, but take a look at our 18-064. Be sure to compare the dimensions with your old part to see if they match.

However, if your window cannot stay open, then very likely your window balances also need to be replaced. If you wish to do this, remove them from the windows and provide pictures the balances, of any stamped codes, and of any attachments at either end. Also, if you could provide the length of the metal channel of the balance (but not any attachments at the ends), this will help us narrow down what you need.

No, you do not require a bottom sash guide unless you're dealing with a specific type of balance.

This looks like either a Series 380 or Series 385 Channel Balance. The only difference between these two Series is the 'depth' of the bottom nylon shoe. With the Series 380 the depth of this nylon shoe is 1", whereas with the Series 385 it is 1-3/32". Compare with your own and see what is best.

I couldn't quite tell from your photos the length of the metal channel (but not including the nylon attachments). You will need that measurement to determine which balance from either Series to select. For instance--and I stress that this is just an example--if your metal channel is 30", and if you a Series 385 Channel balance, then you would select the S385-30. You then need to select a stamp option. Was there any stamped number on the metal channel? If not, you will need to weigh your window sash and match that precise weight with one of the stamp options listed on the product page.