The one unit construction of this lazy susan is only 5/16" thick and can be recessed, which reduces the space to 1/8". The center opening allows for a center post and easy centering. These lazy susans are zinc coated for rust resistance. This 12" lazy susan is intended for up to 1000 pounds and a top with a diameter of over 20". These lazy susans are designed to appear to have a few ball bearings missing. This makes the bearing spin better. This does not affect load capacity.