Case & Chain Knockers with 15 Metres of 8 mm Cable The Case & Chain Knockers with 15 metres of 8 mm cable is a convenient, ready-to-use bundle for cleaning and descaling a wide range of pipe sizes. Supplied in a durable carry case, it includes a Standard Chain Knocker, a StarBit Chain Knocker and 15 metres of 8 mm cable. Includes: 1 x Carry Case 1 x Standard 8 mm Chain Knocker 1 x Starbit 8 mm Chain Knocker 15 metres of 8 mm Cable