Got this off a bagnall and kirkwood listing
Model Outer (mm) Inner (mm) Thickness (mm) No. Coils (mm) Length (mm)
No. 1 21 14.5 3.25 31 280
No. 2 22.7 15.5 3.65 30 291
No. 3 20.8 14.73 3.26 34 304
No. 4 22.62 15.64 3.65 28 252
No. 5 19 13.19 3 32 290
No. 6 19.7 13.3 2.92 39 341
No. 7 20 13.8 3.3 30 255
No. 8 20 13.8 3.3 34 295
No. 9 21 14.75 3.3 27 280
No. 10 21 14.8 3.1 27 230
No. 11 18.8 12.8 3 31 230
No. 12 18.912.6 2.9 36 295
No.13 19.4 13 3.1 39 340
No.14 22.7 15.4 4.12 37 356
No.15 17.53 12.1 3 33 254
Hatsan 19.55 13.4 3.0 37 310mm
5/25 12.5 9.5 1.6 28 240mm