The Wera 8784 B1 Zyklop Bit Adaptor has a 3/8in Square Drive and is suitable for 1/4in hex bits as per DIN 3126-C 6.3 and E 6.3, ISO 1173 and Wera series 1 and 4. It is made from high performance chromium vanadium steel. The quick-release chuck design provides fast bit changes.