Grub Screw Range 3 and 4mm ~ Grub screws for Pinions and anti-roll bar set screws. Grub Screws Typically 3 x 3mm are 1/10th electric pinion grubs and the 4 x 4mm are 1/8th electric pinion grub screws. Longer grub screws are used for various applications with RC models check out our range.