Standard Bobbin Lead (Irish Tension) S10 Bobbin.

Capacity 6-9 ounces

Ratios are: 1:5.5 (slow spinning/heavy yarns), 1:7.5 (medium yarns), 1:10.5(fast spinning/fine yarns)

Fits wheel models S10, S10DT, S51, S51DT, S15, S17 and S75DT.