I bought this for an F1 Mainframe that didn't work out for me. It is not water proof or blood proof, but does a pretty good job. Seems to fit the Mainframe as designed. I had issues with the left side zipper creeping down while carrying the pack. Repeated calls to Eberlestock, left messages, no response. I e-mailed and was advised that if I purchased a J-bag there would be a left side keeper for the zipper included. and that one was not available any other way. I responded that I had just purchased a J bag with no keeper which was why I was e-mailing. No response.