Tool/gauges used to measure distance from underside of string to top of hammer head felt.  This is an important adjustment as too much or too little distance from the hammer to the string will cause the action to play improperly.  Different pianos (even similar pianos with different setups) will use different distances for hammer blow.  Less keydip=less hammer blow, more keydip=more hammer blow.  More hammer travel gives more power, less travel is less power (but often better repetition).  Piano regulation often involves compromise and balance.  These gauges will help. 9 distances - 1-5/8" through 1-7/8" in 1/32" steps.

Ships in a small hardboard box for protection during shipment and storage in a toolbox or drawer (2nd pic).

If you're determining the best regulation setup for your piano, try regulating just five notes, start to finish.  If you like that particular setup, then you can do the rest of the notes.  If you don't and want to try something different, you've only spent the time on those 5 notes and can tweak them until you find the setup you like.

I'm Howard Gustafson and your success with my products is very important to me.  Please feel free to contact me, before or after the sale, with any questions you have regarding this item.  I've been in the piano business as a technician for 30+ years and I'm glad to help.  My contact information is included with each shipment and you can also reach me through eBay.