stamp on channel

If your stamp says 26C and you're positive that you need a Series 385 (which involves making sure your bottom plastic attachment matches the 15-004 and your top matches the 19-005), you probably need the 2630 option (C is the 3rd letter). Verify that by weighing the sliding window sash. For a 26C/2630 stamp, it should weigh between 13 and 19 pounds.