Full Ceramic (ZrO2) Bearings. (Set of 2 of the same size.) *Other sizes are also available. (A small discount will be offered for multiple purchases.) ↓ Specifications: Size Standard: 623 (also known as 1030) Outer Diameter: 10mm Inner Diameter: 3mm Thickness: 4mm Examples of Compatibility: 【Shimano】 ・23 Antares DC MD ・21 Antares DC ・12 Antares ・18 Aldebaran MGL ・15 Aldebaran ・24 Metanium DC ・15 Metanium DC ・13 Metanium ・24 Scorpion MD 200 ・21 Scorpion DC ・19 Scorpion MGL ・17 Scorpion DC ・24 SLX ・23 SLX DC ・22 SLX DC XT ・20 SLX DC ・19 SLX MGL ・22 Curado DC ・22 Exsence DC ・20 Exsence DC SS ・16 Engetsu ・Engetsu ・16 Stile ・Cardiff ・SpeedMaster ・Quickfire, etc. 【Daiwa】 22 Silver Wolf SV TW PE SPECIAL 21 Steez A TW HLC/LTD SV TW All Steez models *AIR TW is BFS only 21 Zillion SV TW 20 Zillion 10 SV TW Zillion TW HLC 1516/1514/SV TW, etc. *The above is for reference only, please confirm the size compatibility at your own risk. The smoothest rotation is achieved when used dry, but when installed in the spool system of a bait reel, a high-pitched "shhh" sound may occur during casting. If you are concerned about this, apply an appropriate amount of oil. (It should quiet down a bit.) *However, because it is full ceramic (the ball retaining parts are PTFE), there should be no seizing like with metal cage & metal ball bearings, even in the spool rotation range of a bait reel (even when dry). In other words, it is a (currently) ideal maintenance-free bearing that does not rust (even in saltwater) and does not require lubrication, etc. Because it is a non-magnetic material, it is easy to install near the brake magnet. Please note that after installing it in a reel, you may not be able to receive manufacturer warranty, so please do so at your own risk.