Since these are the pre-installed runners, remove the side caps at the ends to insert them. TOSO Winpia Curtain Rail Tachikawa Blind, V17 Curtain Rail Fits C-shaped rails. Tire diameter is 6mm. Manufacturer: Tachikawa Blind products Catalog price: 46 yen per piece The tires on runners wear out over time, making them slide poorly. Why not take this opportunity to replace them? Of course, you can also use them to supplement any missing runners. It's easy: insert them into the groove of the curtain rail and then pull out the plastic core above. Thank you for viewing.