The Bluelab Combo Meter is a pH and EC meter from market leaders Bluelab, used by both commercial and hobby growers to great effect.
It's initial outlay is well worth it as they easily outlast other pH/EC pens on the market due to it's robust design and highly reliable and consistent performance.
The meter comes with a 5 year guarantee as standard, and there's a 6 month guarantee on the probes themselves - the probes are also available to buy separately. Very highly recommended.