16 Pa. Code § 83.15
Upon application, a municipality may upgrade its benefits under Article II of the law (53 P. S. §§ 881.201-881.215) by entering into a contract with the Board under the benefit provisions available under Article IV of the law (53 P. S. §§ 881.401-881.413). The Board will not, and the municipality may not, enter into a contract which decreases benefits or which provides benefits in excess of that available under the law or another existing law pertaining to that class of municipality. A plan to upgrade benefits shall, prior to its approval, be determined by the actuary to be actuarially sound. Additional costs or benefit increases shall be the responsibility of the municipality and its member employes based upon the benefit plan selected and approved by the Board.
16 Pa. Code § 83.15