A serrated and curved knife that is useful for eating grapefruits.
It can sometimes be quite frustrating when eating a grapefruit with other utensils. The reason is that utensils are often wide and the fruit portions are more slim. Another reason is because when you try to dig out the fruit you end up "squishing" it more than scooping it. In the end you are basically creating fruit juice than anything else.
A grapefruit knife solves these issues. These knives are shaped for their intended use. The slim and narrow point that slowly widens mimics the shape of the fruit you are eating and the bend in the knife follows the bend of a normal sized grapefruit making it much easier to scoop out the segments.
The edges are serrated. This allows you to slice through and around the fruit segment before scooping it out.
There is not much different from one brand to the next, the tool is almost identical whichever you buy.
Since the design is pretty much the same across brands it comes down to the material it is made of:
Standard: Most metal utensils are made of foodsafe alloys of common metals (think of any spoon or fork in your drawer). For the most part, the material would be stainless steel.
Plastic: We have seen plastic versions of these and we and some are quite interesting. We really like the Norpro squirtless tool (see below).
These knive may come in sets. They often are combined with grapefruit spoons.