Twinring™ Groved Rear Chainwheel (441U-520-48GPOR) by Renthal®. Unique flat face design keeps weight to a minimum and means the TwinRing is as narrow as a regular chainwheel. Flat socket head screws add additional strength to the chainwheel during side impacts. Self-cleaning mud grooves between every tooth on both sides help prevent dirt build up. This top-grade product is expertly made in compliance with stringent industry standards to offer a fusion of a well-balanced design and high level of craftsmanship. Manufactured from industry-leading materials using up-to-date equipment, it ensures everlasting reliability and enduring value. This product is distinguished by total quality assurance, unsurpassed by anybody else.