Yeh but I dont want to be consistantly 15 psi over or under.You know that halfords jobbie is that that digi one because it gets good reviews ah it this one £10 http://www.halfords.com/webapp/wcs/stores/servlet/product_storeId_10001_catalogId_10151_productId_786151_langId_-1_categoryId_255241
So when you get them calibrated do you find that they are out or quite good each time, in my search I have seen the blue point talked about.