They have changed the face of our towns and launched a new sport. Both the young and the old can be seen skimming through pedestrian areas on roller or "inline" skates or racing against each other in sports competitions.

The skaters are carried by eight rollers, four in a row on each skate. This trend has spread rapidly.

High demands are placed on the rollers:

• very low friction for the high speeds required by sports skaters

• good sealing for minimum maintenance requirements

• the ability to withstand shock loads when travelling over uneven surfaces

• long operating life for "hobby" skaters, so that the rollers need replacing as rarely as possible.