99% pure polycrystalline Al203 injection-molding manufacturing process Wondle Series Ceramic Bracket Wondle Roth Ceramic Bracket 0.022" no -hook 0.022" 3-hook 0.022" 3,4,5-hook 0.018" no -hook 0.018" 3-hook 0.018" 3,4,5-hookWondle Edgewise Ceramic Bracket 0.022" no -hook 0.022" 3-hook 0.022" 3,4,5-hook 0.018" no -hook 0.018" 3-hook 0.018" 3,4,5-hook