this magnet- thats talked about here?

[bsa_bob]

I have heard about this magnet, referred to few times being cracked ,etc. How does this benefit my CC. Need to know.. if its worth the trouble,before --(I mount a new speed sensor) to put it in .Also BTW where does it go. behind the sensor?Anything on this? thank you bob s

ps; do i need to put a little silicone or lubricant. on the new sensor so it goes in easier?.