The BK / BF supports are sometimes called “pillow block” style. The screw fixing holes are supplied to the base where your ball screw will work.
The BK final “fixed” support contains two angular contact bearings that provide both axial rotation and support for the ball screw.
The “simple” BF / float has only one standard ball bearing that provides the rotation support at the end of the ball screw opposite where the unit is produced (usually a motor or pulley).
Our level of ball screws are supplied with the machining that will work with these supports without modification.