The difference is pretty clear to me so I am not sure what you mean.
#540 Minoxidil 5% w/o Propylene Glycol
Price: $ 19.00
Quantity and Ingredients: 65 mL. 5% minoxidil (50mg minoxidil/mL) in a liquid base of 50% ethyl alcohol, 30% glycerin, and 20% water
Length of Use: 65 mL is a 1-month supply when used twice daily as directed.
Xandrox 5% w/o Propylene Glycol
#640 Xandrox 5% w/o Propylene Glycol
Price: $ 33.95
Quantity and Ingredients: 65 mL. 5% minoxidil plus 5% azelaic acid in a liquid base of 50% alcohol, 30% glycerin and 20% water.
Length of Use: 65 mL is a 1-months supply when used as directed