I bought these 40" drawer slides because they were cheaper than others. Additional tools and accessories that load onto these slides. The frame that supports the slide is made of 2x6 fir and the slide itself made from 1x4 and 1/2 plywood.Since writing this review I have noticed a request for a width dimension on these slides.Due to proprietary tolerances I have measured the width from 0.680" to 0.740".