Sil 0500 M16 Internal Threading Holder For Size 16 Laydown Threading Inserts Sil 0500 M16 Internal Threading Holder: Neck Diameter = 1/2 Inch With A 5/8 Inch Round Shank Diameter Left Hand Boring Bar Internal Lay Down Threading Holder For Size 16 Inserts K Diameter Left Hand Boring Bar Internal Lay Down Threading Holder For Size 16 Inserts Tmx Toolmex Part #6-Sil-500-M16