Toso Return Fittings - 6 Pieces - Unused These are inserted by loosening the screws on the lace side (window side) of the curtain rail. They help to improve insulation by preventing cold air in winter and warm air in summer from entering from the sides of the rail ⤴️ I think they have an energy-saving effect. [Please refer to the reference photos] They can also be expected to prevent light leakage from the sides of the rail. ⭐️ If your end caps are screw-on, these should work, but please make your own judgment. The items are the red circles in the first photo. [Curtains and curtain rails are not included] ⭐️ Although they are "unused," they may have been taken out of the bag, so please be aware of this. ★ Basically, they will be sent via regular mail on weekdays, so please understand.