It takes 6x6cm frames on 120 film. There are optional adapters for 4.5x6cm plates and 6x6cm sheet film and interchangeable lenses up to 400mm. Standard lens is Xenar 75mm f/3.5, but it offered with Radionar and Victar lenses also.. It has a focal plane shutter. 
There are two models:
Beier-Flex I with speeds 1/25-1/500, and Beier-Flex II with speeds 2-1/500.