ORP is the Oxidation Reduction Potential that your aquarium has. As it can be mistaken for it is not the dissolved oxygen available in the tank as their is a different probe and monitor available for that. ORP is the ability to oxidize which if you are employing ozone on your tank an ORP controller or monitor is highly recommended.
The Neptune Lab Grade ORP Probe is great for any monitor or controller that requires a BNC style connection with a high quality probe. If you are buying a new controller that doesn't include a probe like the Apex lite, adding a new tank and need another probe, or just replacing your worn out old probe look no further.
Lab Grade probes will hold calibration longer, and generally just last longer than standard grade ORP probes.