Does anyone know what these are for?
Saw a different MW today and she asked me to pop one in without telling me what it was for. A quick look on Google suggests the most likely reason was for illegal drugs testing 
Is this standard practice? Or do I just look like a smackhead?
I didn't ask at the time because I didn't want to give her the impression that I had a particular problem with being drug-tested. Just mildly offended curious (and wondering whether I need to start washing before leaving the house)