Designed as a drop in replacement for the weak snap tube holders. Uses the same screw, and optionally can be zip tied. If you're printing from a 21.59 cm (8.50 in) or smaller spool, you can use two. If you're printing from a 25.0 cm (9.84 in) spool, only use the top one. Remove the old holder screw and zip tie. Attaches using the same screw and a 4 inch zip tie.