Used for applying compound to corners prior to installation of tape-on corner bead. Columbia mud heads are machined out of high-tech delrin plastic for a smooth and easy glide. Lay a perfect bead of mud for both Outside 90 Degree, and Bullnose Corner Bead. Locking spring clip is included to keep the head from falling off of the applicator tube or box. Additional ball is included to operate with all Columbia Mud Tubes. Compatible with all major brand angle boxes, Mudrunner, TapeTech Mud Tubes, and Columbia Mud Tubes