... and dustproof.5Newly punch forming fan blade, reasonable angel and reach the max. air flow, mini. Noise.6Double bracing (E style) ... .9Special motor hole wind shield, avoid losing wind to reach the best wind suck effect.10belt type B,thicker and durable ... ,low noise,high resistant.The use rises the tightener pulley organization,the leather belt cannot the loose belt,fall the belt. Design by computer ...