The OPin endpin is a special invention of Linda's; it has acoustically engineered openings, strategically placed and machine-drilled to create a more direct and clear sound on many cellos. The complexity of the sound is preserved and overtones enhanced. The endpin gives most cellos added volume, resonance and projection, and a freer, clearer sound.
If your cello already projects well, and has a clear sound with plenty of overtones, this endpin may not make a huge difference in the sound. However, if you have a cello that sounds 'closed' or 'stuffy', or is not as loud or complex as you would like it to be, this will probably do the trick. To some ears, it sounds like your cello has been mic'd and run through an equalizer.
You can also experiment with spinning the endpin (so that the holes face in different directions) to see what effect it has on the sound, but the preferred placement is to use the most holes facing forward. Veteran cellists at Linda's workshop have tested this invention on their cellos and been blown away by the sound. Comes in 10mm width by 20" length only, with sharpened stainless steel tip. Comes with rubber endpin cap.