So, yup. The Derby. This year it was won by a horse named American Pharoah.
If you looked closely, you might see he was wearing a rather unusual bit. It appeared to have a rubber mouthpiece with spoon-shaped pieces on either side.
This bit is called a - wait for it - rubber dexter ring bit. The mouthpiece has a single joint, but is covered in rubber, which is generally used on a horse that doesn't take a metal bit well. It's actually milder. The spoon shaped cheeks help steel. The ring at the bottom is generally put on a horse that is a little spirited and difficult when being led.
So, if you noticed American Pharoah's odd bit - now you know!
This German racehorse is wearing a similar bit, but in this case with a metal mouthpiece. Image source Softeis via Wikimedia Commons.