You can't trust the air pressure. They show random pressure every time.
Bought in September but never checked air pressure until February, shows low pressure on all double test caps shows low pressure. After removing the cover, the air pressure is normal. I can't trust them to provide proper air pressure now.
Pros
Made in the USA! Typically used on commercial vehicles, RVs, trailers and semi-trailers, but can be used on anything with a valve stem.