I got the now discontinued 2015 version of the Fluid Vest to replace a Camelback pack that was always more than I needed for races and longer trail runs. It is minimalist and perfect for runs up to two hours. I'm average size (for a trail runner) and chose the S/M and the fit is appropriately snug. No movement or chafing and is comfortable, even in 90+ degree SoCal heat. The front pockets fit most handheld bottles or can be used for nutrition, your phone, etc. The upper pockets are great for gels, salt tabs and keys. The main rear pocket fits up to a 1.5 liter bladder but I paired it with the 1 liter Ultraspire and still had room for a lightweight shell. Without a bladder, it works with Z-poles quite well, easy to get them out when you need them but a little hard to get them in without taking off the vest. I've added shock cord to the loops on the back to hold a warmer layer if needed. More versatile than you think. A decent alternative to the more expensive Salomon, Ultimate Direction or Nathan vests. Get it while it's still available. The updated 2016 version looks to have added capacity, pockets and a higher price point.
This review was written in the old system and had content requirements that are different than reviews written today.