MTP Brand 5 inch PSA Backing Adhesive Back Sanding Pad with 5 vacuum holes replaces Porter Cable 13901. This pad takes 5 inch adhesive-back sandpaper discs with five holes. This pad also converts models 333 and 333VS random orbit sanders for use with five holes adhesive-back paper. This part is compatible with - Porter Cable: 332 Type 1, Type 2, Type 3, 333 Type 1, Type 2, Type 3, Type 4, 333VS Type 1, 334 Type 1, Type 2, Type 3, Type 4, Type 5