The shelves dimensions given in the advertisement are true to size. I no longer have to worry about batteries. I had to chose one from Sennheiser Presence, Plantronics Voager Legend, and Jabra Talk 45. Another thing I noticed is the side buttons would be unresponsive or very laggy during mouse movements. He never had that complaint with his underarmour slides, which are probably a higher grade of memory foam. I was advised before buying it! On most electronic muffs and headphones this area is only lightly padded, so eventually the hard plastic pressing on the outside of my ears begins to hurt. I bought 1/2 a size larger and their a bit loosefitting which I wanted. If youre new to these, youll find that riding in place is a weird sensation, because, unlike a stationary trainer, these require you to balance just as you would on the road. I like that I can move my feet around and even dance in these.