Terbium gallium garnet (TGG) is a kind of high performance magneto-optical crystal in the visible and near infrared spectrum, which is widely used in laser technology, optical communication and optical information processing technology. It has high feld constant, low optical absorption coefficient, high laser damage threshold and good optical properties. These excellent properties make TGG crystal an ideal material for magneto-optical isolator. We can provide φ4 inch TGG boule.