Synovex H Implants - 100 dose box Used to help improve average daily weight gain and feed conversion efficiency. Implants contain two pure steroid hormones. Synovex H or S is recommended for use in heifers (H) or steers (S) weighing over 400 lbs. Synovex C is for suckling beef steer and heifer calves (C) over 45 days of age. Aseptically administer implant subcutaneously in the middle third of back of ear.