Stainless steel 1/2" MPT x 5/8" barb fitting that is great for using with 1/2" ID silicone tubing.  Silicone tubing is often soft and very flexible so it is actually a better fit to have a larger 5/8" barb fitting to put the tubing onto instead of a 1/2" barb fitting.  This is also great for using with a magnetic drive pump because it allows for a larger volume of wort to enter the pump thus decreasing instances of cavitation.