No, if it is narrower than your saddle, which it almost certainly is. We have several. Only the bloated XL version is even detectable. It holds a lot. It is arguably the best saddle bag I have ever had. The loop is perfectly designed for a cygo-light or similar tail-light that clips on. The "door" has inner mesh that enables you to pack stuff like money, credit cards, IDs, etc. easily. Roll your tube so that one end is narrower, and jam it in all the way, first. You can get a lot of stuff in it.

I can measure mine if you want. You can get them at REI.