Nathan Replacement Bladder – 1.8 Liter (1.8L) / for Hydration Vests, Hydration Pack. Leak Proof. BPA Free!

I bought this to go inside the Nathan VaporHowe 4L (coral color) hydration vest. The vest says it only takes bladders that are 1.5 L, but this one fit perfectly! The top doesnt stick out or anything. Maybe it would if you had the bladder completely full and had items stuffed into the vest, but as soon as you drank the water down a little bit, it would slouch right in. The bladder is great, I enjoy the shape for running and if you just turn it upside down and suck the air out, it does not slosh at all. Hope this helps!