Filament wound fiberglass airframe made to fit Mach 1 tubing.
 
BT20, BT50, BT55 bands are .5 in thick
 
BT60, 54 mm, 65 mm, 76 mm, 98 mm bands are 1.0 in thick
 
Airframe
ID
OD
BT20
(18 mm)
18.0 mm
(0.709 in)
19.0 mm
(0.748 in)
 
 
 
BT50 
(24 mm)
24.0 mm 
(0.945 in)
25.0 mm 
(0.0984 in)
 
 
 
BT55 
(33 mm)
33.0 mm 
(1.299 in)
34.1 mm 
(1.343 in)
 
 
 
BT60 
(40 mm)
40.5 mm
(1.594 in)
41.5mm 
(1.634 in)
 
 
 
54mm 
(2.2 in)
54.5 mm 
(2.146 in)
56.6 mm 
(2.228 in)
 
 
 
65mm 
(2.6 in)
65.0 mm 
(2.559 in)
67.4 mm 
(2.654 in)
 
 
 
76mm 
(3 in)
76.2 mm 
(3.000 in)
78.5 mm 
(3.091 in)
 
 
 
98mm        
(4 in)
99.0 mm 
(3.898 in)        
102.3 mm 
(4.028 in)

There is a +/- .3mm or 0.012 in margin on all sizing
 
Price is per switch band.