It's always good to have a few spare Handcuff keys around. Mr. S offers a number of 'specialties' keys that will fit most standard handcuffs. Most of them also have the little 'nipple' on the opposite end to push in the 'double lock' button on your cuffs. These Longer length cuff keys make it also easier to hold onto them when opening the cuffs... esp. if you are trying to open them by yourself when they are behind your back.