Air springs with levelling system and vertical adjustment .
带调平系统和垂直调节的气动弹簧撑杆。
Much of the increase occurred during the 1980s and 1990s , and appears to be levelling off in the 2000s .
比率增长最快的是80年代和90年代，而到了2000年以后则趋于平稳。
Despite a recent levelling out after the first quarter 's collapse , the world trade organisation reckons global trade volumes will be around 10 % lower this year than in 2008 .
