BubblHandz® - Midnight Black Piano Hand Posture Trainer

Edges that fit in palm need to radiused more. Very uncomfortable when trying to maintain proper hand position.

Very useful

Took me a second to calibrate but totally changed the trajectory of my playing and posture.

They're great as long as you don't go past the first 5 fingers. Once you tuck your thumb under the bar gets in the way. The idea is great, but it definitely has some flaws