Constructed from 1200D polyester 3M reflective strip One main compartment with mesh inner pockets (large and medium models are expandable) Mounts to seat with two buckled seat straps and one velcro seatpost strap Velcro Straps 7.9x4.3x4.7 (MD)` 60-80 c.i. Black Small (1-100 c.i.)