Package: Chain Guide Material: Aluminum alloy chain guide. The description states it is hard, robust and easy to break. Key benefits - Keeps the chain in place to prevent derailment on rough terrain. - Improves shifting reliability under load. - Aluminum alloy provides a lightweight, rigid construction. Compatibility and size - Compatibility details are not specified in the provided description. Please verify fit with your frame and drivetrain. What it does - Function: Guides the chain to stay aligned during rides and shifts. - Performance: Supports consistent chain retention and dependable operation. Use scenarios - Mountain biking on rocky or technical trails where chain drops are more likely. - Gravel or cyclocross riding with rapid shifts and varied terrain. - Routine maintenance or field use to ensure chain alignment during rides.