Sold by piece by weight. Sizes may look similar depending on shape/thickness. Each Lapislazuli stone has been weighted. 
XS: 4g to <7g
SM: 7g to <10g
MD: 10g to <15g
LG: 15g to 20g
Stones cranked up by Jay Essex and Diana R. Anaya (Dianimal)
Pictures taken both in natural and artificial lighting 
Lapislazuli- Works the Pineal Gland (what people call the third eye) down through bottom of neck, and also the Hipothalamus. Helps Metaphysical Vision- best seeing live energy in other dimensions