The fourth cache in the Felix bound series - see #01 Felix bound for more details.
You are looking for magnetic micro.
At this point, if you don't want to go all the way to Meopham you can cut across via Meopham Madness #9 and #11 to rejoin the "Felix rebound" route that returns to New Ash Green.
After leaving this cache again look north, If you happen to be caching after snowfall in winter you may be able to see the snowcapped peaks of the Essex mountains. During the rest of the year all you can see are the Langdon Hills.