5 Series blocks offer small to medium sized racing and cruising yachts an extremely high strength to weight ratio and oversized sheet capacity. They are true workhorse blocks and will provide years of trouble-free service. Versatile head design has a three-way, built-in locking feature and accepts multiple universal adapters for custom mounting Tough, hardcoat anodized aluminum cheeks with UV protected Delrin sheaves or Delrin ball bearing sheaves Sheave diameter: 2" Pin diameter: 1/4"