This is a complete set of custom Jesel Dogbone Retainers. This is a custom set manufactured for one of the NASCAR teams. We believe this set was designed to align lifters with tie bar style posts. We were unable to find any additional infomation on these special dog bone style retainers. The spacing on the two lifter locations is approximately 1.570" center to center for a standard Small Block Chevy or Bowtie block. As seen in the photos, the lifter locaitons are NOT offset. These are priced very reasonable for the perons who knows what they are and how to use them. Dog Bone Roller Lifters get their name from the O.E. style dog bone shape alignment plates that are bolted to the cylinder block for cam/roller alignment. JESEL's Dog Bone Roller Lifters are lighter than traditional tie bar styles of lifters and can be easily installed in the home workshop using JESEL's Dog Bone Installation Fixture. These roller lifters are ideal for most forms of racing. Note: This listing contains stock photos. Product may vary slightly from photos based on current inventory.