Looking to stop your cold (and hot) air going out your roof? This Battic Door Attic Stair Cover fits folding attic stairs and is designed for 22′′ x 54′′ to 22-1/2′′ x 54′′ rough openings (actual cover size is 21′′ wide x 52-1/2′′ long x 13-1/2′′ deep inside dimensions, 21-5/16′′ wide x 53-1/4′′ long x 13-5/8′′ tall outside dimensions)
This is an older model and does not come with the nicely sewn thermal cover shown on the their website but instead came with a thermal "bubble wrap" foil sheet that you sticks on. We never used it.
Full details of what these are and install instructions are at https://www.batticdoor.com/product/attic-stair-covers

Insulating Attic Door Stair Cover (Ayer)