Various sizes and makes noted in description:
Estes = Estes brand Couplers
Pro Series Couplers are also manufactured by Estes
BMS = Balsa Machining Service
Tube reference:
BT-5 = 0.52" ID, 0.54" OD (Fits 13mm mini engines)
BT-20 = 0.71" ID, 0.74" OD (Fits 18mm "A", "B" & "C" engines)
BT-50 = 0.950" ID, 0.976" OD (Fits 24mm "D" and "E" engines)
BT-55 = 1.28" ID, 1.33" OD
BT-60 = 1.60" ID, 1.64" OD
BT-70 = 2.175" ID, 2.217" OD
BT-80 = 2.56" ID, 2.60" OD
3.0 = 2.93" ID, 3.0" OD
2.0 Pro = 2.0" OD
2.5 Pro = 2.5" OD
Shipping shown is for single largest coupler. We do combine shipping and will refund excess shipping charged at checkout.
Thanks for looking!