These bicycle saddle storage bags are made by Inertia Designs, a prominent bag designer for most of the big brand saddle bags. There is a small internal pocket ideal for a multi-tool and the bag zips closed with a nice durable zipper.

Both bags will fit a tube, tire levers, and multi-tool. If you'll be using 29" tubes or a wide 27.5" or 700c (700x40 for example), the large bag is recommended. The regular is great for standard road bike tubes (700x32c and smaller).

Sizes:

The regular measures 8" long, 2.5" tall, and 4" wide. 

The large measures 9" long, 3" tall, and 4" wide.