EMT conduit already telescopes, but it is a sloppy fit. These pieces "straighten" up the telescoping ability of EMT conduit. Stop tubes can also be used with Locking Tops. Note: These pieces are meant to be glued onto the EMT. Slip Tube pieces are for the end of the larger tube. Stop Tube pieces are for the end of the smaller tube Use both together to keep a smaller EMT conduit piece concentric inside a larger piece. More sizes coming soon!After cutting your EMT to size, make sure to debur the inside and outside of the conduit.