I was looking for a replacement of a much older Protect-A-Bed Bug box spring encasement. Specifically, for a Twin mattress. I assumed that Twin meant 38" x 75" x 9", the numbers appearing on the manufacturer's label (for the older one). I didn't think to confirm these figures for the online offering. I assumed "Twin" implied a world-wide standard. Wrong! The dimensions on the product I received were 36" x 84" x 9". I wanted to try and was indeed able to fit the encasement to my box spring. Of course a little long at one end, but folder over, manageable. Otherwise the quality matches my expectations.