活接头有螺纹连接和承插焊连接两种，活接头，又叫由壬或由任，英文单词为union，是一种能方便安装拆卸的常用管道连接件。活接头由三部分组成，一个特制的八角螺母，和两个特制的螺纹接头，螺纹接头用于连接管道中的两端管子，中间的八角螺母相当于一个管箍将两端管子连接起来，这样可不动管子而将两管分开，便于检修。

塑料固定电缆防水接头PG,M,PG-L,M-L尺寸对照表一、塑料固定电缆防水接头PG型产品型号螺纹规格适用电缆ThreadCableRangeModelsize(mm)PG7PG73-6.5PG7PG72-5PG9PG94-8PG9PG92-6PG11PG115-10PG11PG113-7PG13.5PG13.56-11PG13.5PG13.55-9PG16PG1610-13PG16PG167-12PG19PG1912-15PG19PG1910-12PG21PG2113-18PG21PG219-16PG25PG2516-21PG25PG2513-18PG29PG2918-25PG29PG2913-20PG36PG3622-32PG36PG3620-26PG42PG4232-38PG42PG4225-31PG48PG4837-44PG48PG4829-35PG63PG6342-50PG63PG6332-40二、塑料固定电缆防水接头M型产品型号螺纹规格适用电缆ThreadCableRangeModelsize(mm)M8M8×1.252.5-4.5M8M8×1.251-2.5M10M10×1.53-6M10M10×1.51.5-3M12M12×1.53-6.3M12M12×1.52-5M16M16×1.54-8M16M16×1.52-6螺纹外径ThreadO.DL2(mm)螺纹长度扳手直径ThreadLenghthSpannerSize(mm)A&E(mm）813/12813/12815/13815/13918/16918/16922/19922/19螺纹外径ThreadO.DL2(mm)12.512.515.215.218.618.620.420.422.522.5242428.328..359.37171螺纹长度扳手直径ThreadLenghthSpannerSize(mm)A&E(mm）918/16918/16922/19922/19924/22924/221027/241027/