Fits standard US Langstroth wood (or plastic) medium frames.
The yellow frame rests (at the top of the short sides) are included.
Please note: There are no bottom yellow pieces available for the 6-frame medium boxes.
Very high quality. Pieces are thick, hard, and very tight fitting. I used a rubber mallet to put the boxes together. The mallet didn’t dent the polystyrene at all. Very nice product.