Designed as a two-part system: Part 1 is a T6061 alloy wing that affixes to your saddle and works with a standard or dropper post. Part 2 is a removable and waterproof dry bag. The bag has a scuba-style air-bleed valve to assist with compression while off the bike. The wing stays on the bike; the bag comes off and allows you to pack, compress, and go ride in the snap of a few buckles.