VICMARC VM120/150 25mm Pin Jaws
 
These jaws are used for expansion into small recesses and for firm holding of fine spindle work, such as earrings, chess pieces, etc. they are ideal for turning salt and pepper shakers. To turn very small articles, the jaws can be unscrewed and the backing jaws can be used alone.

The sizes indicated on the drawing are when the jaws form a perfect circle.  VM120 and VM150 chucks provide approx. 48mm of expansion beyond these specified sizes.