These are the Spare Stretcher Bars for across the top of the Nurge Adjustable Needlework Frame that give the width. They are interchangeable with other size bars and screw arms. There are also 3 sizes of adjustable screw rods available depending on the width of the fabric you use. 45cm (17 3/4") 60cm (24") 75cm (29.5") They come in pairs and can be used with any length of fabric. *Most of the manual work making the Adjustable frames is in the stretcher rods, so they may seem expensive compared with the whole frame, they also use a lot more beech wood!