Do I need to replace all four lug nuts at once, or can I mix lengths?

You can mix 60mm and 90mm on the same vehicle if your wheel design accommodates both. This set gives you the flexibility to do that — test-fit on your wheels first to confirm which length seats properly at your hub.

Are the spikes glued on, or do they pull off clean?

Spikes are removable and designed to swap on and off the lug nuts. They're not permanently attached, so you can switch between spiked and smooth looks without tools.

Will these work with my stock wheels, or are they only for aftermarket?

M12 x 1.5 is the standard metric thread on most modern vehicles with aftermarket wheel fitment. Stock wheels may use a different lug nut taper or size — verify your wheel's lug nut requirements before ordering.