yeah, I thought about that.
I was just thinking if you have 4 spacers and you replace the rear axle you don't need 2 spacers, that makes sense.
To match the front and rear wheels he would need adapters for the front so that should open up 4 spacers instead of 2.
Doesn't matter, he's got 2 spacers for sale

. I expect a member who bought these two could also get 2 from Mark for a full set.