Proposal to amend UN Regulation No. 129 to remove rebound head contact from the head acceleration requirement for all Child Restraint Systems. The regulation currently lacks consistency regarding whether rebound head movement is considered in testing. Variations in test bench design cause booster seats to pass in some laboratories but fail in others based solely on rebound contact. The proposal ensures consistency between different CRS types and reproducibility across laboratories with different test bench designs, and aligns with the approach in UN Regulations 94 and 137.