SciCon Anatomico Roller Saddlebag $39.95
You can easily fit two tubes, tire levers, a patch kit, and a multitool, in the Anatomico Roller Saddlebag, but SciCon gives you the option to expand it from 820cc to 1610cc in volume. In its larger form, you can also easily hold energy bars, snacks, a telephone, and other personal items.
Its versatility doesn't stop there either. You can strap a small air pump or foldable tire on the outside of the bag too. The Anatomico Roller Saddlebag attaches to the saddle using the lightweight, quick release SciCon Roller system. It is available in black and reflective silver.
What community has to say
Warning: attaches to seat post
I was looking for a saddle bag that didn't attach to the seat post, to avoid the velcro attachment that rips up lycra bike shorts. I thought SciCon only made bags that attach to the saddle rails directly, but this bag attaches to the saddle rails AND has the typical velcro attachment to the seat post. This is the only SciCon bag I've seen that has this feature. So, although I was excited about the large size of this bag, I returned it and replaced it with another smaller SciCon that only attaches to the saddle rails. This would be a great bag for a touring bike or cruiser bike where you're not wearing lycra bike shorts, though.