Geiger apparel comes in sizes 34 to 56; below is a guide to translating these into U.S. sizes. In general, you simply subtract 30 from the Geiger size to arrive at the U.S. equivalent size.
Geiger Size (U.S. Size Equivalent)

34 (4)

36 (6)

38 (8)

… and so on…

52 (22)

In cases where “Small” to “XX Large” are used, here is the guide:

Small = 34/36 (4/6)

Medium = 38/40 (8/10)

Large = 42/44 (12/14)

X Large = 46/48 (16/18)

XX Large = 50/52 (20/22)