Ronstan S40 Soft Attachment Block - Single Single. With the shackle open cheek plates twist to open the block and a spring loaded ball secures the assembly when closed. Every SA Block features fully machined anodised aluminium cheek plates. Sheaves run on duplex stainless steel hubs and incorporate precision composite journal bearings and thrust washers. The attachment is a Dyneema SK99 soft shackle with titanium dog bone. Specifications for Ronstan S40 Soft Attachment Block: Manufacturer: Ronstan Color: Black Package Contents: Ronstan S40 Soft Attachment Block Ronstan RF47109: S40 Soft Attachment Block - Single Single