A nice spare to have for when you forget to put threadlocker on your wheel hexes and the wheels fall off along with the drive hexes and pins. The grub grub screw is used to inside the stub axle and actually holds the drive pin in place so you do not lose them. The axles on my J3 Speed already have the grub screw, but a spare never hurts.

A nice spare to have for when you forget to put threadlocker on your wheel hexes and the wheels fall off along with the drive hexes and pins. The grub grub screw is used to inside the stub axle and actually holds the drive pin in place so you do not lose them. The axles on my J3 Speed already have the grub screw, but a spare never hurts.

A nice spare to have for when you forget to put threadlocker on your wheel hexes and the wheels fall off along with the drive hexes and pins. The grub grub screw is used to inside the stub axle and actually holds the drive pin in place so you do not lose them. The axles on my J3 Speed already have the grub screw, but a spare never hurts.

PERFECT! At first, I didn't know what the grub screws were for. It screws inside the wheel axle and pushes against the wheel joint pin so that the pin doesn't slip out when a wheel is removed/falls off. Use a 1.5mm allen wrench for these screws, and put some loctite if you want. ;-)

PERFECT! At first, I didn't know what the grub screws were for. It screws inside the wheel axle and pushes against the wheel joint pin so that the pin doesn't slip out when a wheel is removed/falls off. Use a 1.5mm allen wrench for these screws, and put some loctite if you want. ;-)

PERFECT! At first, I didn't know what the grub screws were for. It screws inside the wheel axle and pushes against the wheel joint pin so that the pin doesn't slip out when a wheel is removed/falls off. Use a 1.5mm allen wrench for these screws, and put some loctite if you want. ;-)