Works on most nail or screw in the tread portion of the tire. Actually, your tire pressure warning system will most often alert you to low pressure in a tire well before it goes flat from a screw or nail slow leak. Almost all of my flat tires in my previous car, showed up first thing in the morning, when I went out to drive to work - with either a 'low tire pressure' warning, or a flat tire. In all the cases, if I checked tire pressure and if within 10 lbs of normal, I just drove to Discount Tire for a free tire patch, or if flat, I just added air, then drove to the tire shop. Just carry a good tire air pressure gauge in the glove-box. If you don't need to use the sealant, you can just use the air compressor to add air to a low tire - as I have heard the sealant ruins the TPMS sensor in the tire, which then has to be replaced. No flat tires yet in my i3. Also had a MINI Cooper for five years. No spare tire, no tire inflation kit, Came with run-flats, which were terrible, and I switched them out for reg. tires. Never in 5 years had to change a tire. Picking up a nail would just get a slow leak, take it in to a tire shop, and get it fixed.