The topeak dynapack dx is a larger version of the dynapack and offers near trunkbag space without needing a rack it features an expandable top to hold a helmet shoes and other large objects topeak dynapack dx features divided main compartment one weatherproofed zip pocket attaches with qr clamp fixer 7 clamp fits 254 to 349 diameter seatpost capacity 97 litre590ci 3m reflective strip redlite clip 225x20x155cm 890g topeak about the brand topeak is the world leader i