详情描述：
要求粒径是 2-20um要求粒径是 2-20um要求粒径是 2-20um要求粒径是 2-20um要求粒径是 2-20um要求粒径是 2-20um要求粒径是 2-20um要求粒径是 2-20um要求粒径是 2-20um要求粒径是 2-20um
要求粒径是 2-20um