The Brilliant Tools BT024006 Bit adapter set includes four sizes: 1/4" (6.3 mm), 3/8" (10 mm), 1/2" (12.5 mm), and 3/4" (20 mm). This robust and versatile set is ideal for a variety of screwdriver applications, providing compatibility across different driver sizes. Perfect for both professional and DIY use, it ensures a secure fit and efficient torque transfer.