A pair of pretty small, but extra strong wheelchocks to be used with 19" wheels in emergency situations. Pack these up with the (scissors-type) car jack lifting kit you take in your car along with the spare wheel. Use the wheelchocks on the opposite of the wheel that needs to be replaced before you start lifting the car, to ensure stability and prevent the car from rolling backwards (or forwards) while you twist the jack up. Use only on flat surface. Not to be used to stabilize the car on ramps! 

It's small enough to fit in the bag/box of the jack, yet still effective to avoid accidental falls of the jack, especially when adapter pads need to be used between the car and the jack (on most EVs).

Print in something strong like ASA, to withstand extreme temps and mechanical stress. Use 5 wall loops, 5 top and 5 bottom shell layers, and 50% infill for extra strength.