Review on Nathan 1.8L Replacement Bladder for Hydration Vests & Packs - Leak Proof, BPA Free! by Mar Pacora

I bought this to wear my Nathan VaporHowe 4L vest (coral). The vest says it only accepts 1.5 liter bottles but this one fits perfectly! The top doesn't stick out. Maybe it would be if you had a full bladder and stuff stuffed into the vest, but as soon as you drink a little water it settles right away. The bladder is great, I love the way it runs and if you just turn it over and suck the air out, it doesn't squeeze at all. Hope that helps!