Evoc is a German brand that comes from mountain biking, known for its backpacks with back protection and bike transport covers. Its frame luggage follows the same principle: keeping the contents in place and protecting them from impacts and splashes, on routes where the bike is constantly shaken.
Evoc started with transporting fragile equipment, and this culture is reflected in its luggage. A hard shell protects fragile items carried on a bike better than a soft bag, which explains the structured walls on handlebar and top tube formats. A convertible bike bag to backpack meets the need to get off the bike and continue on foot without transferring everything.
The choice depends on the location, as each area of the bike can hold a different weight. A small frame bag is sufficient for keys, the phone, and a spare inner tube on both a city bike and a gravel bike. Beyond that, you need to lower the weight and bring it closer to the bottom bracket.
Start with the contents, not the capacity. A camera or full-face helmet requires a structured wall and padding, while a jacket and gloves can fit into a bag with soft sides. Then check three points on the bike: the routing of the cables, the remaining space for water bottles, and the rear wheel travel when the suspension is in use. These are the factors that determine if a model is suitable, never its volume.