a more modern implementation is the parabolic leaf spring. this design is characterized by fewer leaves whose thickness varies from centre to ends following a parabolic curve. in this design, inter-leaf friction is unwanted, and therefore there is only contact between the springs at the ends and at the centre where the axle is connected. spacers prevent contact at other points. aside from a weight saving, the main advantage of parabolic springs is their greater flexibility, which translates into vehicle ride quality that approaches that of coil springs. there is a trade-off in the form of reduced load carrying capability, however. the characteristic of parabolic springs is better riding comfort and not as "stiff" as conventional "multi-leaf springs". it is widely used on buses for better comfort. a further development by the british gkn company and by chevrolet with the corvette among others, is the move to composite plastic leaf springs. nevertheless, due to missing inter-leaf friction and internal dampening effects, this type of spring requires more powerful dampers or shock absorbers.