How good to these things work? And what are the skematics for this thing?

A Studor is a brand of AAV or air admittance valve. They work fairly well but will eventually require servicing so they can not be sealed up inside a wall or structure. Some city codes will not allow a AAV so check before considering further.

how good to these things work? and what are the skematics for this thing? They do exactly what they're designed for. They vent the fixture that they're installed on. See image. Regards, Tom

It is so called "One Way Vent". It allows air In but it will not vent out sewer gases . For this reason, you should not use this type of vent on Sewer Ejectors.