Rolling bearings use rolling elements to maintain the separation between moving parts to reduce rotational friction and support radial and axial loads. These elements can be one of the following types: ball, cylindrical, spherical, barrel, needle, spindle, or tapered. Sealed bearings are lubricated with oil or grease in the bearing factory, while open and shielded bearings are meant to be lubricated in place, with periodic reapplication of lubrication, based on use. The shield protects the working parts of the bearing from environmental debris that may be introduced and could reduce the ball bearing speed and lifespan. Rolling bearings are used in a range of applications from agricultural machinery to conveying equipment, robotics, dental equipment, elevators, rolling mills, ship rudder shafts, and aggregate crushers, among others. Product name: Dining Table Turntable Bearing Structure: Aluminium Alloy Colour: silver Advantages: smooth, heat-resistant, safe and stable Size (diameter): Φ40cm(15.7inch), Φ44.2cm(17.4inch), Φ50.6cm(19.9inch), Φ60cm(23.6inch) Product carrying capacity: 160kg/180kg/180kg/220kg Products include: 1× rotating tray Bearing PS: 1.If your turntable can not be turned freely, you can try some lubricant and synthetic spray lube on it from the side holes and the gap between outer and inner ring. 2.The turntable bearings are linked by steel beads, it may sound during rotation. Loading some weight on it will effectively reduce the sound.