If you’re on the line between sizes, you have the option of either length. Which length you choose will depend on how much space you like in a sleeping bag, as well as whether you’ll need to store extra gear in your sleeping bag. If you are 5’3” or 6’, you will fit comfortably in the bag designed for your height (in this case, the Small or Regular), but if you'd like a little extra room -- particularly if you are looking at a winter or expedition sleeping bag -- a longer bag will give you an extra 6" to stow fuel, electronics, water, clothing, boot liners, and any other temperature-sensitive items. If you're looking at a 3-season or summer bag and would like a snugger, more thermally efficient fit, go with the shorter length. If you are taller than the stated bag length, we recommend going with the longer size.