I capitalized heavy as the unit is about 5 pounds. They apparently overcompensated for the complaints of ease to break. The main arm is 5/8 dia and the second is 1/2 dia  - plated steel. The stays and stay screws are spring steel with plastic finger tabs. The spring-loaded adjustment on the secondary arm is really cool and easy to use. The magnetic base has about a 15-20# holding force. It is plenty to hold the indicator and stand in any position. The previously mentioned would be my only complaint - it is large and heavy. Movement on the dial indicator is smooth and accurate. The type of tool you would expect to find attached to a D8 caterpillar or locomotive engine... Size could be an issue. I have not checked but a job like measuring ring and pinion backlash could be an issue due to the tools size. For my machining purposes it is very usable and quite accurate. For $22 I am very happy.