Material Version 330: Housing: Steel, zinc-plated.  Ball cup:
Steel, case hardened.  Ball: Steel, hardened.

Material Version 340: Housing: Steel, zinc-plated.  Ball cup:
Steel, case hardened.  Ball: Stainless steel, hardened, Material No.:
1.3541.

Premium ball transfer unit, for low noise pollution and long service
life. With felt seal. See also the tolerance rings:

They permit more generous tolerances in the mounting hole. Conveying
speed max. 2m/sec. Temperature range -30°C to +100°C.

Note: Due to unevenness of the running surface, there are often
only three rollers carrying the weight.

Therefore the chosen load rating should equal at least one third of the
load.

Max. distance of ball transfer units = edge length of the object divided
by 2.5.