Here is the relevant section from my email that gives basic details of the work:
(I note your interest in upgrading your cartridge and you may like to consider a modification we carry out to upper end cartridges. The modification involves the removal of the aluminium cantilever, machining an abutment and bonding a low mass white sapphire cantilever together with our ultra low mass Paratrace profile diamond. The reduction in overall mass allows the cartridge to trace groove modulations with greater accuracy resulting in maximum retrieval of information)