In-line skates (often called Rollerblades after the popular trade name) are a type of roller skate used for inline skating. Unlike quad skates, which have two front and two rear wheels, inline skates have two, three, four, or five wheels arranged in a single line. Some in-line skates, especially those for recreation, have a "stop" or "brake" which is used to slow down while skating; most have a heel stop rather than the toe stop, particularly indispensable for inline figure skating.

   Aggressive inline skates
The modern style of in-line skates was developed as a substitute for ice skates, for use by a Russian athlete training on solid ground for Olympic long track speed skating events. Life magazine published a photo of American skater Eric Heiden, training for the 1980 Olympics, using such skates on a Wisconsin road.
During the late 1980s and early 1990s, Rollerblade, Inc., a company founded by Scott and Brennan Olson in Minneapolis, Minnesota, widely promoted inline skating; they were so successful that their trademarked name Rollerblade became synonymous with inline skates.[
A skate is composed of a boot, worn on the foot. To the boot is attached a frame, which holds the wheels in place. Bearings allow the wheels to rotate freely around an axle. Finally, the rubber brake typically attaches to the frame of the right foot.

   An inline skate designed for artistic roller skating
There are different types of inline skates for different types of skating such as aggressive skating, speed skating, Inline hockey and artistic inline skating. Those differ in the boots, frames and wheels that are used.

   Think about what kind of skater you are before you buy. Rollerblade bearings perform differently, depending on the kind of skating they were made for. Determine whether you use your skates for tricks, speed performance, long distance or sports like hockey. This will help you narrow the choices to find the right kind of bearing.

   Consider your wheels. It's important to couple bearings with the right wheels. Many skaters find that hard trick wheels are best with slower, more durable bearings. The opposite is true for big, soft wheels: a faster bearing will maximize rollerblade performance.

   There are two main types of bearings: standard 608 and mini 688. Standard 608 bearings are more commonly used in most rollerblades, including recreational and roller hockey models. Mini 688 bearings are smaller and can wear out faster than 608 bearings. Ensure that you get a wheel and bearing combination that matches up when you purchase new bearings. In most cases, you can increase your overall speed by upgrading to a higher ABEC number.