Rear shocks

Can anyone tell me the correct nut size for the upper rear shock absorber mounting nut? Replaced both mine today and both nuts have completely stripped threads. Surprised they don’t come with the new shocks! Managed a temporary repair with two stainless nuts & spring washers but will feel happier with nylocs.

Sorry, it’s a 92 200tdi 110

M12.
Nothing special about them but LR part number is RYH500510.

Cheers Litch. Only reason I asked is the ones I fitted took a different spanner size to the ones I took off!