This is part of our NFN Nora's First Night series, one of our "Winter Friendly" series, which are designed to be easy walking in all weathers. See NFN-1 On Yer Bike for more details.
You are looking for a tube about twice as long as a film canister, with magnets. PLEASE replace on the lower bar of the two options, otherwise it is too high for some cachers to reach.
If you prefer a search, please note that our hints tend to be fairly explicit