This is experimental, however I have had great results. Once you have the correct amount of oil it works perfectly.
Shock's tested:
https://ercmods.com/collections/parts/products/axial-scx24-aluminum-threaded-mini-micro-shocks-front-rear
Hot Racing Shocks:
https://ercmods.com/collections/new-arrival/products/reservoir-friction-damper-shocks-axial-scx24
O-Ring Kit used:
https://www.amazon.com/gp/product/B07WRF9YYC
My measurements came in at 5mm and 3mm outer diameter.
Tools:
1x 1.5mm hex driver
1x Micro tweezers
1x Pick
1x Team Associated 35wt shock oil
1x Team Associated Green Slim grease
Leather hole puncher: https://www.amazon.com/gp/product/B00KY3WAK6