Perfect size and hydrogels flow well. Cap is terrible, rotates to open in the wrong direction (taking the cap off instead of opening the pour valve when trying to rotate it open). With cap updates, this would be perfect for IM triathlon bike fueling and ultras.

I keep mine half filled at all times with Honey from my bees here in AZ. Works great! Never leaks, and is either in my pocket when riding bikes, or ski touring, or in my chalk bag when I'm climbing. Its great because it lets me kneed my honey and warm it up when its cold and get it flowing. It is very thick since it’s only lightly filtered so it’s full of very corse crystals up to 1mm in width at most times. Flows through the nozzle great!

I love that I can refill this and not have to mess with single use gels. I've never had an issue with it leaking and will most definitely be purchasing more refills in the near future.