4 Quick Clamps to stay firmly attached, 2 on each side and are adjustable. 
Waterproof with water tight zipper.
Great for those quick rides to keep a jacket and your trailside repair kit with you.
Large size has two straps inside to hold a spare battery, rain gear, trailside repair kit or anything you need to enjoy your ride. 
 
12" x 8" X 6.5"