Amazon is selling this at a $10 discount, normally $24.99 and now at the lowest all time price of $14.99
What is it? If you use your DSLR for video you have probably noticed that zooming while shooting can be tricky to do smoothly, the zoom rings tend to be small and stiff. With this accessory you can zoom gracefully by moving the arm instead of grabbing and twisting the ring. Same for focus if you do macro photography/videography and need to carefully set up focus for tight shots.