Matrix Dressage Ortho Impact Half Pad Inserts are sold in pairs to fit the pockets in your matrix half pad. Matrix Biokinetic Inserts offer customized back protection for the horse using the T3 principles of ergnomic design and advanced technology. Every Matrix Half Pad comes with a velcro spine to accomodate inserts so the rider can switch inserts for diferent horses or different needs using the same half pad. Using separate inserts for the left and right side of the pad allows space in the middle for spine clearance and free movement of each side of the horse's body for greater comfort. Sold in PairsOrtho Impact: For general riding and schooling, especially beneficial for stabilizing the saddle and compensating for horse conformation problems; for riders who need back support. A layer of ultra-light, high density PoronR XRDTM minimizes concussion; medium density viscoelastic foam offers stabilizing support for both saddle and rider. PoronR XRDTM with MicrobanR is high performance open-cell foam that absorbs 90% of the energy from the impact from the saddle on the horse's back as well as minimizing the energy bounce back that a rider experiences landing in the saddle, allowing for a more secure seat. Viscoelastic foam offers maximum cushioning protection without restricting range of motion.