Formula Series, Racing Series, Valkyrie Series, King Series, Sentinel Series and Tank Series. The simplest trick to distinguish the difference between the six series is the size. F, R, V, K, S, T is equivalent of what we're familiar with, size of the garment: S,M,L,XL,XXL,XXXL.

Formula Series: S
Racing Series: M
Valkyrie Series: L
King Series: XL OH/KS
Sentinel Series: XXL OH/SJ
Tank Series: XXXL OH/TS