Absolutely great for overhead tricep extensions! The hammer grips will ensure proper form. Also great for Hammer Curls. As you can see in the video, they also kick ass for skull crushers and front shoulder lifts. Remember that incorporating small changes to your workouts like different grips, or unilateral versus bilateral (one or two hand) will give you a fuller workout and avoid muscle adaptation and plateauing.
There are also others to choose from on Amazon like some with olympic sized ends if you want to use the olympic weights or non threaded versions. I have a non threaded one that I use with spring clamps. I find it faster to simply slide one of those clamps instead of having to screw on a cap.