Like other apparently I am very satisfied with this product that improves glide and especially protects and maintains the ropes well. Bye bye oxidation, strings and therefore its dirty rotten after a while. Preventive and curative effective too! A lug around with his guitar so. I received the package "metal" very nice. I have not really tested for the maintenance of the key because I remain faithful to the lemon oil to the ropes but it's really good, I think this product will pay for itself alone, I do not know how long it will last but a priori I would buy.