Sold by piece by weight. Sizes may look similar depending on shape/thickness. Each AAA Ruby stone has been weighted
Pictures taken both in natural and artificial lighting 
XS: 9g to 10g
SM: 16g to <20g
MD: 20g to 30g
LG: 31g to <41g
XL: 50g to 53g
Stones cranked up by Jay Essex and Diana R. Anaya (Dianimal)