The wood is Red Oak which was ebonized with a vinegar and steel wool fluid inside and outside. The size of the openings range from 5/8" thru 1-1/4". All are 1/8" - 3/16" wall thickness. All were buffed with tripoli and carnauba wax.
The sizes are;
4.5" dia x 4.5" tall, end grain
4.5" dia x 7" tall, end grain
4" dia x 6" tall, end grain
6" dia x 3.5" tall, side grain
7" dia x 4" tall., side grain