At first I thought how could Freud have created an adjustable groove bit, with the seemingly single cutter, and make it adjustable. Then I discovered that it really was two cutters that were sandwiched together. Their carbide tip is a lot wider than the plates that hold them. Additionally they are offset, so when they are sandwiched without any spacers, they are just like having the one bit. With the included spacers, you can adjust that groove cutter to a nice range of sizes.
Additionally the two large cutters that make up the tongue bit are adjustable with the spacers that are provided. They are stacked on the bit so you don't have to go looking for them when you want to make a change.
I have a lot of Freud bits, and I have bought all of them from Amazon. The price and convenience can't be beat. The one complaint that I have is that Freud does not wrap these bits in a way that protects them from a UPS shipment. Do you know what UPS stands for? Unbelievably Pulverized Shipments. :-) With carbide tipped bits, which are super brittle, rolling around in the box, after they come loose from the snap together plastic carrying enclosure, they are left to do battle with one another. Consequently, check your faces for defects when you get them. Amazon has the greatest customer service.
All in all a great set of bits, highly recommended.