Series 40 Ball Bearing Block - Double - Swivel Head. Features: Low friction Acetal or Torlon bearing system; lightweight cheek cut-outs for easy bearing maintenance; swivel shackle head for full 360° rotation. Sheaves run on Acetal or Torlon ball bearings providing high performance and low friction. The 2-stage ball bearing system provides consistent performance over the full load range. Applications: mainsheet, halyard, vang, spinnaker control lines on off-the-beach catamarans, one design classes and sportsboats up to 8m (26ft). Additional product information: Material: Plastic (Acetal/Torlon bearing materials); Bearing Type: Ball Bearing; Compatible lubricant: Grease. Item dimensions (L x W x H): 5 x 3 x 2 inches. Item weight: 3.2 ounces. Model: RF40200.