Because MSR changed the cap design on the DromLite Bag, it doesn't work well with the 4 liter molle bag opening for the nozzle. I was able to get some old caps that can work with the molle bag opening, but I suspect those won't be available for long. The only caps are much better in my opinion. The new one has a string for attachment which makes it hard to tighten and loosen. Also, as mentioned, the new cap is smaller profile and has wings. This may be good for hikers or other uses, but not good if you actually want to use the pouch opening on the 4L molle bag.
Fits in my pannier pouches just fine.