2mm neoprene and mesh backing. Includes two HDPE (high density polyethylene) water bottles. Water bottles hold up to 170 ml. (5.75 Oz.) each. Water bottles are held in place with elastic straps. Bottles have push pull caps. Padded back panel with mesh. Keep hydrated during your workout. Zippered pocket in between bottles. Adjustable webbed belt with plastic hardware. Perfect for running, hiking and walking. 14" W x 4.5" H x 2" D