Right inbetween our small and large backpacks you will find this medium size. It has an extra pocket on the front, waterproof lining with a handdrawn pattern and adjustable shoulder straps with a cheststrap. On the inside you'll find an elastic band that serves as a bottle holder and a pocket all over the back that closes with velcro. There is also a name tag to put your info. 

sizes
— body - 23,5 x 13 x 32 cm
— front pocket - 19,5 x 9,4
— shoulder handles - maximum length 67 cm
— elastic band inside - 2,5 x 11 cm

materials
— body - recycled PET bottles
— front pocket - 50% cotton 50% polyester
— handle - cotton
— zipper - matt white YKK
— lining - waterproof nylon
— buckles - matt white metal