Powdering Tube is for sprinkling of "maru"-type metal powder onto final coat of urushi.  It comes in different tube sizes and mesh sizes.  We have selected this size that is suitable for gold and silver powders we carry. 
 
This is probably one of the iconic tools of maki-e art, besides the maki-e brush.  
 
Bamboo spinkling tubes are handcrafted by artisans.  Nowadays, they are made with aluminum tubes for lower cost.  It is getting difficult to procure bamboo ones.  Bamboo is better as it gives the right friction for your fingers to hold and tap to release the powder.  And it won't cause static to your metal powder (not a fun scene). 
 
Best to keep the tube separately for different kinds of metal power to avoid cross-contamination.   And practice makes perfect.  
 
Bamboo tubes runs on a number system made with different size mesh fabric, suitable for various sizes of gold and silver powder.  This one matches the size of gold and silver powder we carry in our store.