Measured size of xs
H 32" x W 20" x D 8". It's a lot larger than I expected. Doing the math brings it to 83L but the little pack sack says 55L-65L. It's definitely less than 83L because it tapers (I don't have good perception of volume numbers so I can't give you a guesstimate of it's volume size). I don't have a backpacking backpack but from the looks of it, it is definitely larger than a typical school backpack and won't fit my friends medium backpacking backpack. With my best guess I ordered it hoping it will work for a bag I have that measures 16"x18"x8". I ordered the black xs and it didn't have the cinch cord that are in the pictures. Just an elastic band with a loop on one side and a velcro strap on the other. I'm waiting for customer service to email me information if the other xs in the warehouse have the same setup. **Update** They said the black model does not have the cinch cord but the blue does like the photos.