The Salomon S-Lab Sense Ultra Set is a ultra lightweight running hydration vest. The Sense Ultra Set comes with 2 x 500ml Salomon soft flasks. This is such an amazing hydration vest to wear. It literally feels like a snug fitting running top. Pocket placement and design are ingenious and factors in just the right amount space to carry essential items. The S-Lab Sense Ultra Set running vest weighs in at just 250 grams.