Collins Bus Corporation (Collins) is recalling certain 2011-2018 Collins SL, SH, DH, DE, and TH school buses, built on Promaster chassis, equipped with CE White/HSM SB11-30″ series, standard, unbelted, school bus seats, or SB11-30″ series school bus seats with lap belts only. The foam in the knee impact area of the lower seat back may not absorb enough impact in the event of a crash. As such, these vehicles fail to comply with the requirements of Federal Motor Vehicle Safety Standard (FMVSS) number 222, “School Bus Passenger Seating and Crash Protection.”