Fly High Pro X Series Side Fat Sacs (Pair) Fly High Pro X Series Side Fat Sacs - 48"x12"x12" - 260 lbs. Each - Fly High Pro X Series Side Sacs were designed to sit along the side of the engine compartment on inboard boats. They are small enough to leave you some room to walk. These sacs are the most demanded on the market for their durability and ease of use. Priced per pair!