The Coffee Tumbler pocket attaches to the side pocket attachment points on either side of the pack. It is adjustable on the sides and length to fit a variety of different coffee tumblers, up to the largest Starbucks makes. It fits quite snug in the pocket and is very stable on the pack. We venture to say it would probably would not fall out even if your pack fell off at speed.
It easily mounts to the side pocket attachment system on the side of every Velo Transit pack and the Metro 20 and Retro 20 panniers.
It fits on the side of Metro 20 pannier.