These spacers are designed to prevent your weight plates from banging up against the mounting bolts on your plate storage pegs.
These fit typical storage pegs that measure 1.9" in diameter (slightly smaller than a barbell). This is the size used by Rogue Fitness.
This model will fit very loose on the REP Fitness storage horns, and will not fit at all on Titan Fitness products.
These will not fit over an Olympic barbell.
Be sure to measure your setup to see what size you need. If you need a size not listed, let me know and I can work with you.
Q: What size spacers do I need for the Rogue Vertical Plate Tree 2.0?
A: This is how the weight tree looks in stock form. The head side of the bolt is shorter than the nut side, so your plates will hit on one side if you use 30mm spacers. If you want to keep your weight tree in stock form, 1x30mm and 1x40mm spacer should work.
If you are a little more crafty and would like to use equal sized spacers on both sides, you can buy a couple of 5/8" flat washers and stick them under the head of the bolt (see below). This will shorten the bolt on the nut side enough that you can now use 30mm spacers on both sides. McMaster-Carr part number 92141A035 should work, but you can also grab some at your local hardware store.
To be 100% sure on fit, I always recommend measuring yourself.