One of them, these protective helmet covers called Guardian Caps.

其中一种是保护性头盔罩，叫做守护帽。

Among the recommendations are that all first-class cricketers in Australia be compelled to wear protective helmets that meet stringent safety standards when facing fast balling.

建议包括澳大利亚所有一级板球运动员快速击球时必须佩戴满足最严格安全标准的保护头盔。