This is a Boca 14x25.4x6mm Radial Bearing. This bearing is intended for use in a Nitro Engine with compatible dimensions. This bearing is open to allow oil to lubricate it during use.
The purpose of a radial bearing is to reduce rotational friction and support loads. This is achieved by using two races to hold the balls and to spread the load through the balls. As the bearing race rotates it causes the balls to rotate. The ball provides for substantially less rolling resistance and coefficient of friction than if two flat surfaces were rotating.