On Electron tubes you can do one short functional test for a some minutes. If not satisfied, please turn off the tubes, and let us know by email, latest the next day after you received the package. After this you can return them in the next 7 days. (So not use electron tubes for 7x24 hours, and send them back without reason). Original printing will start to darken after some minutes, when the glass gets hot. Changed appearance of the printing is a "no return" reason, but this will not happen when you do only one short test on them.
Capacitors and transformers can not be returned in general.
Wires that we have cut off the roll for you.