The Pro version has no advertising. This app converts from inches to metric (millimeters) and vice versa and is invaluable to anyone that has to deal with both American (Imperial) and metric tape measures, rulers, wrenches, sockets and drill bits. It supports both fractional (e.g. 5/8) and decimal (e.g. 0.625) inch values and converts them to the nearest tenth of a millimeter. The developer of this app used to work as a handyman and the capabilities provided are well-suited to everyday 'practical use' rather than scientific applications. The app provides four distinct 'pages' each with a distinct capability: Page 1: Fractional inches to millimeters conversion, and vice versa, with easy input of numeric values using iPhone-style 'spinner' dials. Page 2: Decimal inches to millimeters conversion, and vice versa, using an ultra-simple calculator-style user interface. Page 3: Provides a table showing the nearest common millimeter values to any fraction of an inch from 1/32" to 1"; this is very useful when you have an American (Imperial) bolt to turn, or hole to drill, but you only have metric wrenches and drill bits. Page 4: Provides a table showing the nearest common fractional inch values to any metric value from 0.5 to 25 millimeters; this is very useful when you have a metric bolt to turn, or hole to drill, but you only have American (Imperial) wrenches and drill bits.