Ronstan Series 30 Utility Block - Double Tube Rivet. Hollow rivets in the block heads can be fitted with shackles which can also be used to add a becket for extra purchase. Specifications for Ronstan Series 30 Utility Block: Manufacturer: Ronstan Color: Black Features of Ronstan Series 30 Utility Block Lightweight durable construction Economical Maintenance free Applications:Vang cunningham and trapeze retriever systems on dinghies Leech line tackles bunk adjusters etc on larger yachts Materials:U.V. stabilized Acetal sheaves Grade 316 stainless steel cheeks Sheave :29mm(1-1/8")Max. Rope : 10mm(3/8")M.W.L.:350kg(770lbs)B. L.:500kg(1100lbs)Weight:40g(1.4oz) Package Contents: Ronstan Series 30 Utility Block Ronstan RF417: Series 30 Utility Block - Double Tube Rivet