The nominal 8x8x16 block dimensions are actually the standard CMU dimensions of 7 5/8″ x 7 5/8″ x 15 5/8″.
Omni Block is manufactured on the same machines as standard CMU and are of the exact same mix formula as well.
Omni Block units have approximately 7% more material content than standard CMU. Therefore, if a locally produced medium weight standard CMU weighs 32 pounds then a medium weight Omni Block will weigh 34 pounds (note that there are usually three classifications of mix design (normal, medium or lightweight).