Domino Spacer

My kids like to set up dominos to be knocked down, but the set they have only came with one spacer; so I printed more. I printed it with 4 walls and 40% infill because I like the heavier feel, but I suppose you could print it lighter for a quicker print. The dominoes we use measure 24mm x 7.5mm x 48mm (H5 brand, found on Amazon)