The size 4 lb has been on DISCONTINUED. We apologize for any inconvenience. Finish Line Pure MSM is used to treat a variety of illnesses in horses, including chronic muscle soreness, epiphysitis, acute laminitis, pleuritis, recurring digestive tract disorder and arthritis. Ultra Pure 99.9% Source of bio-available sulfur. Veterinary interest in MSM (methylsulfonylmethane) has increased over recent