Sizing

Our sizing is the Australian Standard with letters.
This is measured by the inside diameter of the ring.
 L(16.4mm) - M(16.8mm) - N(17.2mm) - O(17.6mm) - P(18mm)
Q(18.4mm) - R(18.8mm) - S(19.2mm) - T(19.5mm) - U(19.8mm) 
V(20.2mm) -W(20.7mm) - X(21mm) - Y(21.4mm) - Z(21.8mm)