Set mine up to zip onto the inside zippers of my bat wings and it works great, when it’s empty it’s nice and out of the way and when full, bat wings are still easily accessible. Keeps water out like it should, seems durable enough (scratched it on a fence that tore my jacket but didn’t harm the bag). I would recommend to anyone with a mainframe.
Eberlestock zip on dry bags kept my gear 100% dry on Unimak Island Alaska for 3 weeks in October!