Some bike helmets are getting better and easier to adjust, thanks to technological improvements appearing at all price levels. But several other helmets failed our tests because the buckle broke--a recurring problem with bike helmets we've noticed for years.

Most adult helmets in our tests, and others costing as little as $30, now use in-mold technology, in which impact-absorbing foam is bonded to the outer shell. After a crash, it's easy to see whether the helmet is dented and thus needs replacing. That's not always the case with helmets whose shell is taped or glued to the foam. The shell typically bounces back after a crash, so a damaged liner can be hard to see.

Most helmets now have easily adjustable stabilizing straps to create a snug fit; many helmets for young riders also have buckles designed to avoid pinching the skin.

WHAT'S AVAILABLE

One top-selling brand is Bell, which also makes models under the Giro brand. You'll also find helmets from Fisher Price, Louis Garneau, Mongoose, Serfas, Schwinn, Specialized, Trek, and W.

Bicycle helmets come in the following types:

Adult. Some models offer a "universal fit," which means they come in only one size with an adjustable band inside. Others adult helmets come in distinct sizes. Whatever your choice, try on the helmet in the store before you buy it to make sure you're getting a good fit. Hinged-snap strap glides, which ease strap adjustment, are a plus, as is a rear stabilizer, which helps keep the helmet in place by cradling the back of the head. We also like in-mold technology, in which impact-absorbing foam is bonded to the outer shell. After a crash, it's easy to see whether the helmet is dented and thus needs replacing. That's not always the case with helmets whose shell is taped or glued to the foam.

Most of today's models are well ventilated.

All bike helmets should be replaced after an impact. And consider replacing any helmet after five years.

Price range: $25 to $140

Youth. These are similar to adult helmets, but are sized smaller for heads 53 to 57 centimeters in circumference. Look for one with good fit, along with the features discussed for adult helmets. Parents will also welcome a buckle guard, which helps prevent the buckle from catching the skin on a child's chin as you fasten it. Note that older youths may fit into smaller-sized adult helmets.

Price range: $20 and $45

Toddler. Sized even smaller for young children, these helmets provide added protection for the rear of the head, though they aren't as well ventilated as most adult and youth versions. Look for one with a buckle guard. And make sure the helmet fits your child now--not when he or she has grown into it.

Any helmet is better than no helmet. But choosing and using one properly can improve your odds of avoiding injury.

HOW TO CHOOSE

Try it on before you buy. If you need help getting a good fit, consider buying your helmet at a bike shop, which may offer better service than other retailers.

Don't lose your cool. If you ride a lot, look for a helmet that did well in our ventilation tests (Ratings are available to ConsumerReports.org subscribers). Many youth helmets aren't well ventilated, so an avid young cyclist might do better with a smaller-sized adult model that excelled in this measure.

Want a multisport helmet? Be careful. "Skate style" helmets, which cover more of the head, look like they'd be appropriate for other sports, but many are not. Only helmets whose sticker says they meet skateboard and snowboard standards are best suited for those sports. Helmets that meet skateboarding standards, for example, must withstand multiple impacts.

Know when to discard it. With all but a multiple-impact model, replace your helmet if you crash and hit your head.