Report on the third inter-laboratory study evaluating the repeatability and reproducibility of particulate emission factors using GTR 24 (1st amendment) across 14 laboratories worldwide. The study assessed laboratory proficiency in brake particulate matter and particle number emissions measurements for light-duty vehicles, testing two low-metallic brakes and one low-emitting NAO brake using the WLTP-Brake cycle. Inter-lab coefficient of variation for PM₁₀ was 10-15% for low-metallic brakes (4.5-8.5 mg/km emission levels) and 30% for the NAO brake (1.5 mg/km). Intra-lab repeatability for PM₁₀ was less than 5% for low-metallic brakes but higher for the NAO brake. A success rate of 94.8% was achieved after applying quality checks, confirming GTR 24 suitability for regulatory testing. The report provides recommendations for GTR 24 amendments including friction work calculation methodology, torque quality metrics, sampling probe setup standardization, and residual torque limits.