MDPE

Medium density polyethylene (MDPE) is a type of polyethylene defined by a density range of 0.926 - 0.940 g/cm3. It is less dense than HDPE, which is more common.
MDPE can be produced by Chromium/Silicon catalysts, Ziegler-Natta catalysts, or metallocene catalysts. MDPE has good impact and drop resistance characteristics. It is also less sensitive than HDPE. Stress crack resistance is better than HDPE. MDPE is commonly used in gas pipelines and fittings, bags, shrink film, packaging film, carrier bags and screw closures.
In the UK, Black (or blue) MDPE is often used for water and wastewater pipes, and may also be referred to as " black alcatene