The BF "simple/floating" support has only a standard ball bearing that provides rotational support on the end of the ball screw opposite of where the drive occurs (typically a motor or pulley). It can only take radial loads and the bearing can move freely in axial direction through the floating housing. It has only one angular bearing as opposed to BK end support which have two angular bearings.
The BF Floating Ballscrew Support Units, or used in combination with the BK Fixed Ballscrew Support Units. For example for a BK15 the counterpart is the BF15. Both BK/BF end supports are sometimes referred to as "pillow block" style
The Bf12 Ballscrew simple support is used with the ballscrew SFU2005 (SFU20xx series) It is assembled of: