Thanks, yes I am aware of that sizing, in the meantime I've learnt that my drive side doesn't loose probable because has been used a thread-locker, also the cause been probably what www.sheldonbrown says about the right threading in the right side been prone to loose.
In the park tool site also i've seen that I would need an adjustable type, in opposition to a cartridge type, but it seems that the adustable type is older and I don't know of any one.
At least I've found all I need in bikeparts, Thanks and cheers.