454.1.3.1.9 states that "Fencing consideration shall be given to the U.S. Consumer Product Safety Commission (CPSC) Publication, No. 362, March 2005, guidelines available from CPSC.gov; OR Sections 454.2.17.1.1 through 454.2.17.1.8. 454.2.17.1.2 states, in part, that ..."Openings in any barrier shall not allow passage of a 4-inch-diameter (102 mm) sphere." Therefore, a 4" limitation is applicable to commercial pool fencing.