Last time I needed replacement SGS-5 stylii, I had the option of going to Boron, was informed there was a tad more warmth w this option. I remain unsure about the fussiness of the SDS-6 stylii, hence have stuck w the SDS-5. What's now happened is that the full potential of the Boron SDS-5 is realised w the more nuanced and tonally full sound.
However I believe the Boron option is not standard issue.