These spacers are designed to prevent your weight plates from banging up against the mounting bolts on your plate storage pegs.
These fit storage pegs that measure 1.75" (44.5mm) in diameter. This is the size used by REP Fitness.
This model will not fit on Rogue Fitness or Titan Fitness products. These will not fit over a barbell.
A variety of sizes are available for purchase. Be sure to measure to see how much clearance you need.