EVOC's Seat Pack Boa makes for useful extra storage on your bike; and it doesn't affect your riding, even when it gets rugged! This is an on-bike storage option that offers all the familiar top quality and functionality that EVOC is known for. - Adjustable capacity due to roll-top closure - Dropper post compatible - Soft TPE seatpost protection - Flexible main compartment closure that adjusts to bag size - Boa Fit System for easy and secure fixation - 100% waterproof