I bought a house and found 3 of these channels but all the other ones had been removed I measure the windows for the one that I don't have any do but I will need all associated parts to them as well I can send more pictures of inside the window but I maxed out at 5. The channels have numbers stamped in them as follows; 13-3 bsi rs and 20-4 bsi tr. I have one large window that the tracks look the same but I wasn't able to find and channels for but I do have the measurements. There's a total of 4 windows 1 small to
Medium and 1 larger window