20 4 Size: 4mm Features: -Material: Vanadium steel.-Polished ring.-Chrome-plated.-Square drive as per DIN 3120 - C 6.3, ISO 1174, with ball retaining groove.-Hand-operated, knurled grip.-Often used in Industry.-Depth of head: 0.08" - 0.4".-Drive connector square (female): 0.25".-Drive connector square (female) nominal size: 0.25". Dimensions: -Dimensions: 0.98" H x 0.26" - 0.79" W.