An easy way to carry plenty of spares and tools with this large lightweight saddle bag from ortlieb its integrated tool free system makes switching the pack between bike extremely quick and simplethe waterproof pu coated nylon and cordura is well sealed with a roll closure supported further with a pair of elastic straps making sure the pack is tightly secured every ride whatever youre carryingthis is the larger version of the seatpost bag which at 4 litres capacity could even replace a back