Nylon Spacer or Bushing . This spacer is designed to adapt the wheel hub of launching trolleys, reducing the diameter from 35mm to 20mm . Made of durable, thick nylon for long-lasting friction, it ensures optimal rolling performance for launching trolleys. This spacer is 20mm long and fits 37cm wheels (references YT-R2 or OPT10786_BK). Two bushings are required per wheel.