The Tris-Compatible Flat pH Sensor, order code FPH-BTA, $99 is more durable than the regular pH sensor, but it still needs to be handled with some care. Both sensors have glass parts that can be broken. The regular pH sensor has a hand blown globe-shaped tip, and the flat pH sensor has a glass shaft with an exposed glass disk at the end. Since the PH-BTA has more exposed glass, it is typically easier to break. As an additional note, if the Flat pH electrode is broken, the FPH-BNC can be purchased as a replacement piece whereas the PH-BTA needs to be completely replaced.