This optional spring makes the Monarch handpiece even more of a dream for ultra-fine engraving and shading. Many top engravers consider their Monarch handpiece ideal for fine work just the way it is...with its standard spring. But this optional spring is so easy to install (less than 15 seconds) that it makes sense to try one. You'll be amazed how efficient this spring makes the Monarch handpiece: only 8 PSI air pressure is required. And, the control you'll get when doing microscopic fine work is incredible.