The cranking amp rating – depending on the size of the engine of your vehicle(s) but usually the higher the better.

Voltage – most of the car batteries are 12V but commercial trucks, RVs and machinery can have up to 24V. Check your battery for the voltage.

Cable length – again, depending on the size of the car and the size of the jump starter. With small jump starters, the cable length is usually between 10 and 12? – just to reach both terminals easily but with bigger car jump starters you might want to have longer leads (around 60?) to ensure comfortable and safe operation.

Based on your other needs you might want to check whether the jump starter has an integrated flashlight, USB ports, 12V outlet or a compressor which might save you in other situations.