This is a replacement 1.5L Hydrapak reservoir for the Gnome Tank Bag.
It features an insulated removable hose with twist on/off valve. The Slide-Seal closure quickly opens up the entire top of the reservoir, making filling and cleaning a snap. You can even turn it completely inside out!
The reservoir is made by Hydrapak from puncture & abrasion resistant RF welded-seam TPU.