I make my blocks from pine. They are sold as a pair. This wood is durable but soft enough to be kind to finger joints. This “standard “ size is 3 inches high, 6 inches long , 3 and 3/8 inches wide. I make every set by hand so there can be an 1/8th of an inch difference in any dimension. I do my best to make them all to these dimensions. I have tested every set of blocks that I produce and I have personally had no issue with 1/8 of inch difference. :) I can make custom sizes as well. There is a non slip rubber bottom. I and my students have used these blocks on lots of different floor surfaces. $50.00 +HST