These have one purpose and as they have one purpose they have only do one thing and that is to lock out potential electrical energy from being released by the system being locked out. This they do very well and they are durable. The key with this product is it only works if all parties work together and do their part. The device itself is worthy and it does its part. You can count on it to do what it was designed. Getting all who use it to do their part is another issue altogether.