Truly the best monkey fist jig on the market, hands down.  The X Jig will allow you to use nearly any size ball, marble, or bearing.  From a 1 inch ball to a 5.5 in ball. 

This is the monkey fist jig to end all others.    

The great thing about this jig is the fact that you can use any ball.  Simply loosen the sliding bars, place the ball of choice in place and hand tighten the bars to lock the ball in place.  

Please watch the video to fully understand the versatility and design of this amazing jig.