To improve fuel economy and reduce cost, automakers have been removing the heavy full-sized spare tire from most new cars. Fewer than one in 10 cars has a full-size spare anymore, according to a Consumer Reports survey. More than half of new cars have temporary space-saving spares, but for the remaining percentage of cars without any tire on-board, you’ll want a sealant kit.

There are three distinct types: Cans that combine sealant and air pressure for partial inflation, liquid stand-alone sealants and deluxe kits that include an air compressor capable of fully inflating the tire. The compressors, available separately, can also be used to inflate bicycle tires, pool toys and sports balls. If you can afford the complete kits, it’s probably the best bet. The sealants claim they won’t harm your newer car’s Tire Pressure Monitoring System (TPMS).

Even if your car does have some kind of spare, it’s possible it’s deflated over time. And if you live in an area with a lot of rough roads, you might think of using tire sealants as a preventative measure—they can be another layer of protection against small punctures. Here are the best options in three categories.

If you trust the automakers (at least on inflating tires) then this is the kit for you. It’s used or recommended by GM, VW/Audi/Porsche, Mercedes-Benz and Peugeot. The kit includes a 12-volt compressor that plugs into your power outlet. The compressor attaches to a 15-fluid ounce can of “eco-sealant,” which the company says will wash out with water after the tire has been professionally patched. The kit will get your tire back up to full pressure and it has been shown effective to patch holes of up to a quarter inch. An LED light for nighttime use is handy. The kit comes with a storage bag, inflator and various adapters. There’s also a budget version of this kit with some assembly required.

The Slime kit has a reassuring, step-by-step design that actually guides novice users through a tire inflation. The sealant is built into the kit. Attach the nozzle to the tire stem and the 12-volt power, dial in “air plus sealant,” press the green “on” button and inflate to the recommended tire pressure using the very useful built-in gauge. Slime sealant is good for holes of up to a quarter-inch. Note: Some Slime sealants actually require the removal of the tire’s valve stem, which is an annoying task; the company’s Thru-Core Emergency Tire Sealant does not need that step.

The key with a sealant like this is to consider it a low-cost emergency stop-gap measure to get you to a repair shop without driving on a flat and causing terminal damage to the tire’s sidewalls. The sealant will partially inflate the tire and seal it temporarily against further leaks. The advantage is low cost—three emergencies for $20. The product is non-flammable and can be cleaned out with water.

This stuff works. It has the advantage of staying permanently liquid which makes cleanup easier. It’s good against porosity leaks and punctures from nails, thorns and other sharp objects. With corrosion inhibitors mixed in, it can also be used as a preventative. The label says “Stops leaks before they happen.” If there’s a drawback, it’s in having to position the tire and then remove the valve stem with the (included) tool before usage.

Forbes Wheels separated the market into three categories:

We evaluated of the tire sealants and kits through the ratings of critics and users, online reviews of users of the products with supplemental information manufacturer fact sheets. The right product depends on your needs and whether you have a portable air compressor.

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