This category comprises double-walled corrugated cable protection sleeves buried in the ground and QZK connectors protecting cables laid in open trenches. They are highly resistant to compression and cracking. The sleeves are intended for installation on sites with low mechanical load. They can be laid directly in the ground. The double-walled corrugated pipe satisfies standards applicable to cable sleeves laid in trenches specified in the Regulation of the Minister of Infrastructure of 26 October, 2005. Each pipe in the drum is provided with a QZK connector for effective connection.