The Fast Eddy Bearings - ARRMA Granite GROM 1/18 Monster Truck Sealed Bearing Kit is a complete 16-piece rubber-sealed chrome steel bearing replacement set. 
It replaces all factory wheel hub, differential, and drivetrain bearings on the 1/18 ARRMA Granite GROM 4X4 RTR to restore smooth rolling efficiency and block out dirt and moisture.
Total Count & Sizes (16 Bearings Total):
12x7x11x3mm sealed bearings (used in wheel hubs and differential outdrives)
4x 8x12x3.5mm sealed bearings (used on inner hubs and main center driveshaft supports)
While packaged specifically for the 1/18 Granite GROM RTR, this exact 16-bearing combination (twelve 7x11x3mm and four 8x12x3.5mm) matches the standard bearing layout across the 4WD GROM lineup (including the Typhon GROM and Mojave GROM).