Substitute 3 PK balls for a #2 Master Pin to Construction Key a Kwikset pin tumbler lock. Construction keying allows the builder to have a key that opens the locks during the construction phase. When the homeowner takes possession of the house and uses their key for the first time, these balls roll out of the pin chamber and collect in a side chamber. This changes the combination and prevents the builder key from ever opening this lock again. These are factory original PK balls. 100 per pack.