Silicone grippers

See the link to this below

Optimum machining to give the lightest weight without compromising stiffness

If you love gravity type riding and are looking to upgrade

Blackburn Outpost Elite Seat Pack with Dry Bag - Black eBay Silicone grippersA bikepackers delight, this bag will mount and come off easily while keeping all your stuff nice and dry. Who's this for: Riders looking for a great alternative to a backpack or paniers for their epic treks into the hills or commutes to work. Things you can carry: Spare clothes, tools, spares for the bike, just about anything really. Mounting locations: Designed specifically for saddle mounting, and it can even mount on full suspension bikes and bikes