Ingeniously powerful patented (US Pat. No. 9,610,487) tennis swing training aid for forehands, backhands and volleys. The product dramatically improves tennis strokes by setting the proper 90 degree angle between the racket and the forearm which is critical to (1) developing effortless power and (2) reducing the chance of tennis elbow injury by transferring the impact force from tennis elbow tendon to wrist.FOREHANDS and BACKHANDS: As the body turns to start the forward swing, the arm goes forward, but the racket head actually goes back to form a 90 degree angle with the forearm (racket lag). Maintaining this 90 degree laid back position until contact is so critical in hitting powerful forehands and backhands. With the Permawrist product, the wrist is held back by the elastic cord to achieve the proper 90 degree angle. If you try to flick your wrist in an improper swing motion, our product’s flexible cord will resist the wrist motion.VOLLEYS AND SLICES: The secret to the pros' volleys is that the racket is locked relative to the arm at nearly 90 degrees and they maintain that locked L-position throughout the swing. By contrast, many amateur players erroneously try to break or flick their wrist in trying to generate power and under-spin. Our PermaWrist training aid will help you maintain the L-position throughout the swing. If you try to flick the wrist, our product’s flexible cord will resist the wrist motion. Same principles apply to slices.VIDEO: Search for "permawrist" in YouTube for demonstration.RELATED PRODUCT: Try our SnappyWrist product for a softer, tactile way to feel the wrist positions. Click the "AA Swing" link at the top under the product title.