These codes refer to plastic KAM snaps sizes:
T1 = size 14 (approx 9mm or just under 3/8")
T3 = size 16 (approx 10mm or just over 3/8")
T5 = size 20 (approx 12mm or 1/2")
T8 = size 22 (approx 14mm or 9/16")
T15 = size 24 (approx 15mm or just under 5/8")
Not sure which size you need? Visit our Snap Sizing Guide.