Strida Magnet Keeper
Strida part number 336-8 is the Strida magnet keeper. This is the part on the left side in the center of the Strida rear wheel that the Strida front wheel magnet connects to when the Strida bike is folded. There is a small allan set screw in this part that is used for adjusting the magnet holding strength.
When replacing this part you may also consider replacing the magnet keeper bolt, part 379, the axle washer, part 469 and the three nylon wheel washers part 376. The other part in this assembly is the Strida magnet sleeve part 338.
Scrolling down this page will provide you with photos and links to the related parts.
Strida parts diagram can be found on page 14 of the Strida Manual downloaded here.