Guóbiāo (国标) — literally “national standard” in Chinese (国 = national, 标 = standard). GB is a mandatory national standard (强制性国家标准); GB/T is a recommended voluntary national standard (推荐性国家标准), where T stands for tuījiàn (推荐 = recommended); and GB/Z is non-binding guiding technical document (指导性技术文件), where Z stands for zhǐdǎo (指导 = guiding).