The Straight Arm is a half swing golf drill tool that improves ball striking consistency by minimizing left arm swing (or right arm, if you're left-handed) on the backswing and keeping the player's focus on the position of the body and leading arm through impact. It is available in 2 sizes. The small/medium will fit most juniors and adults. I (Dane) am 5'9" and 165lbs. and would use the small/medium. I could also use the large but it's a little bulky for me by comparison. Only get the large Straight Arm golf swing trainer if you have big arms. Chose blue or pink when checking out. The pink Straight Arm cast is only available in the small/medium size. Many Golf Instructors Use Terms As Like Right Hip To Left Hip - Swing To 3 O'Clock To 9 O'Clock * Feel The Correct Shaft Angle At Impact * Fits Right And Left Hand Golfers * Learn The Correct Lead Arm Position Without Tension * Promotes Swing Path Down The Target Line * Prevents Chicken Wing * Practice Year-Round Indoors And Outside * Promotes Correct Hand Position At Impact * Improves Shoulder Turn In Your Backswing * Can Be Used Hitting Golf Balls * Improves Accuracy