S17 IRT Bobbin - Unfinished - 3 speed

This bobbin is the same size as the Standard bobbin, but it is unfinished.  recommended for the S17, S15 and S75 wheels, who were all sold unfinished.  ratios: 1:5.5 / 1:7.5 / 1:10.5, volume: 670 cm3 (42.4 cubic inch)

Item # SA0103