The Matrix Endurance Series is specifically designed for endurance riding to offer the maximum protection, support and breathe-ability required for intense long distance riding. The 'Woolback' is 100% fleece, specifically engineered for equestrian use. High moisture wicking, the resilient pile provides superior pressure relief over countless washings and allows continuous air circulation. 
The bottom is bi-level 1" pile under the saddle and 1/2" pile behind the leg for improved heat dispersal. The top layer of innovative ETC fabric provides a non-slip, breathable surface that is stain resistant and easy to clean.
This pad comes complete with Ortho-Impact inserts. Thess inserts are a dual protection dynamic performance insert with an ultra-light, ultra-thin layer of 5mm high density XRD technology which absorbs 90% of the impact along with 13mm layer of medium density viscoelastic foam offering musculoskeletal cushioning. Ortho-Impact inserts offer maximum cushioning protection without restricting range of motion for the horse while minimising the shock felt by the rider, providing back relief. 
Velcro spine opening allows access to inserts.
See images for pad measurements.