Instruct: Classify the given Amazon review into its appropriate rating category
Query: Clearance is CRITICAL!

I purchased this to replace the OEM rear sight with a night sight on a Glock 43. The threads were lubricated with oil and the first attempt to remove the sight resulted in the unit's threaded pusher assembly falling apart. On reassembly and inspection I determined the pusher jaws were too close to the top of the slide (my fault) as evidenced by very slight scuff marks on the slide. After increasing the clearance between the slide and pusher jaws the unit worked flawlessly. The unit did not come with written instructions however a Google search returned videos and written direction.