LIGNTWEIGHT AND DURABAL MATERIAL: Made of ultralight elastic nylon,spandex and polyester fiber, breathable mesh back and shoulder strap,that's very lightweigh comfortable and durable and Adjustable Straps always Make you Have a Comfortable Fit. Let you Enjoy your Outdoor Activities without more Bulking. REFLECTIVE STRIP DESIGN: Front and Back Reflective Strip Design, ensure safety in any light at night during sport; Suitable chest circumference: M/L: recommended chest circumference 90-102cm / 35.43-40.15 inch; L/XL: recommended chest circumference 102-115cm / 40.16-45.27 inch. FIT YOU WELL: Ergonomic designed vest-shaped bag coming with adjustable waist strap and high elastic chest strap. so it can fit most body sizes and keep high stability.This backpack can be used for more than just hiking.It is suitable for almost all outdoors activities such as running, riding, camping, marathon, etc. MULTIPLE STORAGE COMPARTMENT: Designed with large space,you can carry everything you need with the water backpack. Super pocket design that your water bottle, phone, keys, foods can easily stored in the front pack pockets, and bladder or other items can be held in the back one. ✅PACKAGE INCLUDES: 1*Backpack IF THE SIZES OVERLAP, IT IS RECOMMENDED TO PURCHASE A BACKPACK THAT IS ONE SIZE LARGER. REFLECTIVE STRIP DESIGN: Front and Back Reflective Strip Design, ensure safety in any light at night during sport; Suitable chest circumference: M/L: recommended chest circumference 90-102cm / 35.43-40.15 inch; L/XL: recommended chest circumference 102-115cm / 40.16-45.27 inch.