So I've been looking for an easy and cheap solution for filling water bottles with my new sawyer mini filter that would prevent me from spilling water all over the place and I came across these the other day;
https://blumatsystems.com/product/61/Bottle-Cap-with-Blumat-8-mm-barb
Available here
I ordered a few (5 and shipping was $5) and using the Sawyer in a gravity or squeeze configuration with some hose I picked up at Home Depot this adapter works pretty well. The diameter of the barb is about 0.31". Not bad for an adapter that costs only $1 and fits on most water bottles.


