You can choice your size, we include the emeral like says in the Cyprian book
 
Great Protection
Prayer:
 
San Cipriano Prayer "Dedicos Señor Poderoso Alfa y Omega. Substance and spirit of all creation, the memory of my soul, waiting for your divine protection, in how many works to perform on this day " It should be used on the index finger of the right hand It is placed on the stone man in the morning and the Prayer is said Protect from all treachery and all harm and gives you a wisdom equal to that of King Solomon and gives you a clear intelligence.