Features Drop in upgrade component Improves accuracy and range Durable rubber construction Designed for Flat and R-hopping Smooth interior, no locating ridge or hop mound Provides a longer, even, smooth contact surface against the BB Ideal for use with Prometheus flat-hop nubs Compatible with almost all Airsoft AEG barrels Optimized for Flat and R-hopping Manufacturer: Prometheus Specifications: Hardness: 50 degrees Compatibility: Most R-Hop or Flat Hop capable Airsoft AEG hop-up units Material: Rubber