4120 x 1 + 4121 x 1.  XK120 Lower Ball Pin Brass Seat (early type). Sold as one upright Set with 4121 matching spigot ring insert for locating the lower ball pin cap.

Late XK150 may feature the brass cup variant. Original Number C3025. C3024

NOTE : The early O.E. type ball pin seat design was made from a 'newly' developed brass material, known in the day as 'Morganite' ( made by Morgan Crucible Co. of Swansea) that was factory fitted to XK120 and also late run XK150 (exact recorded data of fitment is vague). In the period between they used a deeper cup (with integral spigot) made of a compressed asbestos fibre material known as "Ferobestos" (made by Tenmat of Manchester) which we now replace with a similar deep dish nylon cup ( SEE : 4141 ) which is a superior, modern alternative material.

This may explain some original XK caps not having a grease nipple fitted, as it was not in the Ferrobestos materials design to require re-greasing.

Morganite inserts will require a grease nipple fitting to the cap, SEE :  4313  & 4172