I just installed the Groovetracer and concur 100% with Zoltarcat's findings. I installed this beautifully machines counterweight on my Zeta tonearm which fortunately has the same size end stub diameter as the Rega (.5 inch) for which the Groovetracer was designed. Beside improvements in frequency response extremes, the most significant improvement for me is sound space reproduction. By comparison, the stock Zeta sounded somewhat constricted and lacked depth. The Groovetracer has opened up a door into the music never experienced in my system. There is a bloom to the music that extends floor to ceiling, wall to wall without loss of focus or expanded images. Just the opposite, although the sound space has expanded to huge proportions, the actual images are incredibly tight and defined. I would strongly encourage any Rega, Zeta or other tonearm owners that have the ability to mount this counterweight give it a try, I don't believe you will be disapointed.