Here's some info that Spiral Groove sent me ,
The Centroid has been designed to locate large, adjustable mass distribution close to the unipivot bearing for a range of cartridge weights, yet, unlike lower mass designs, provides adequate mechanical loading and lateral stability of the unipivot bearing design without the need for an alternate stabilizing device. This focus on centroid location and mass distribution close to the bearing also minimizes the moment of inertia of such large mass, leading to responsive yet stable behavior in reaction to stylus and cartridge forces. Our "Balanced Force Design" indicates a wholistic approach to design that allows mechanical resonances to be channeled in both frequency and amplitude into relatively benign "quiet spectral corridors", away from both musical energy and the normal mechanical errata from record warps, eccentricities etc. A freely moving and classic unipivot execution is essential for the stabilizing benefits of the design to be maximized. The unique aspect of the Centroid is that the pivot point is a fixed point and level with the record surface. VTA is adjusted by raising and lowering the arm body on the pivot pin of the bearing so changing VTA does not change the pivot point relative to the record. Anti-skate is accomplished via a thread and weight system with two very important details. 1. The thread of the anti-skate weight attaches to the arm body and the point of contact is height adjustable. This is important as the arm body changes relative to the pivot point when changing VTA, it is important to place the anti-skate force at the pivot point. Attaching the anti skate force above or below that point will result in unwanted force that can result in azimuth changes as the stylus encounters the varying degrees of skating force across the record. To that point, the skating force curve across the record was carefully analyzed. The Centroid anti skate device has been designed to provide force that follows the skating for curve to provide varying degrees, and therefore uniform anti skate all the way across the record. A fluid damping trough is machined into the arm board and the height adjustable set-screw that plunges into the silicone can be lifted entirely out of the fluid if desired.
Arm is mounted.