Hydro Flask Stainless Flat Cap

Purchased this lid / cap so I could seal up my 21oz hydroflask. Works well - keeps things liquid tight and hot for quite a while. I've been ski touring with the bottle and cap system in my pack for a full day and my tea was still pleasantly warm at the end of the trip. Only thing to consider is this cap works with the "standard mouth" size.

There are some complaints that the o-ring doesn't stay on very well. I haven't had any issues with this yet.

I had a pretty similar experience to the other reviewer, I've also found that the plastic ring does not stay in place which, in my opinion, make sit somewhat inconvenient to use. But it doesn't leak, so it does do its job!

I personally think the original standard lid with the 21 oz or 12 oz works better and is more convenient. I wanted to try this on mine to have something that is not plastic but do not like the ring around the top. the ring has to be applied above the thread or it does leak and moves to be removed for cleaning etc. If you don't like the plastic option this is worth it. As far as the low profile and stainless steel option it wasn't necessary for me in this case.