What makes a good reining spin?

A good reining spin is fast, correct, cadenced, and centered around a planted inside hind foot — and all four of those qualities must be present for the spin to score well, because a spin that is fast but incorrect, or correct but slow, does not demonstrate the training quality judges are looking for. The horse should turn through its shoulders, stepping the inside front foot across and in front of the outside front foot with each revolution, keeping the body aligned and the hind end anchored rather than drifting or pushing outward. Cadence means the spin has a consistent, rhythmic tempo from the first revolution to the last rather than starting slowly and speeding up, slowing through the middle, or losing rhythm as the horse tires. The horse should stay soft in the bridle throughout the spin rather than bracing against the rein or leaning on the inside for support, and the shoulders should move freely and willingly rather than being pulled around by strong rein pressure. The stop of the spin is as important as the spin itself: the horse should stop exactly when the rider asks, with no extra steps, no drift, and no loss of balance at the completion. A spin that runs past the requested stopping point, or that requires the rider to visibly counter the horse's momentum to stop it, costs points and reveals that the horse is ahead of the rider rather than responsive to the cue. Speed in the spin is a product of correctness built through progressive training — the horse that understands the pivot, moves the shoulders freely, and maintains cadence will naturally develop speed as its strength and understanding increase, while the horse that is rushed to speed before the form is correct will show holes in its foundation every revolution.