Instruct: Classify the given Amazon review into positive or negative sentiment.
Query: JET Heavy duty universal mobile base

The base is well made, assembles VERY easily and quickly but has a major flaw - the LOCKING wheels do not lock well enough to prevent the saw from moving when you cut heavy material. This is dangerous and makes accurate cuts of larger material impossible. The rotating casters are the worst offenders.I'm disappointed because it is a well made unit and Jet usually produces good quality products. As an engineer I view this as a design flaw rather than a quality control issue.