MGTF Shock Absorber Top Lock Nuts.
The top nuts can easily get damaged or seized and it's advisable to replace when you have removed them with new nuts.
These are M10 x1.25 pitch which are different to a stock M10 metric nut.
Two are used on each shock absorber and are sold in pairs. Order 4 pairs if you intend to remove all 4 shocks. Sold as a pair.