Stop worrying ahout calibrating your electronic devices - these badboys are the only affordable way to check your blood alcohol level on the go. Redline are the only brand of disposable breathalysers that have passed Australian standards - so you know it's good. Used by government departments in Australia and across the world - even the US Armed Forces use these. Cheap enough to throw in your bag before a big weekend. Accurate enough to let you make the right decision. Stay safe out there!