MDPE (Medium-Density Polyethylene) straight compression couplers are used to join two lengths of MDPE pipe together in a straight line. These couplers come in various sizes, including 20mm, 25mm, 32mm, 40mm, and 50mm. Here is a brief description of each size: 20mm: This MDPE compression coupler is designed to join two 20mm MDPE pipes together. It is commonly used in domestic water supply systems and small irrigation systems. 25mm: This MDPE compression coupler is designed to join two 25mm MDPE pipes together. It is commonly used in domestic water supply systems, irrigation systems, and some industrial applications. 32mm: This MDPE compression coupler is designed to join two 32mm MDPE pipes together. It is commonly used in industrial applications, such as water treatment plants and chemical processing plants. 40mm: This MDPE compression coupler is designed to join two 40mm MDPE pipes together. It is commonly used in larger-scale industrial applications, such as oil and gas pipelines and large water treatment plants. 50mm: This MDPE compression coupler is designed to join two 50mm MDPE pipes together. It is commonly used in large-scale industrial applications, such as municipal water supply systems and wastewater treatment plants. In general, MDPE compression couplers are made of durable materials, such as brass or polypropylene, and are designed to provide a secure and leak-free connection between two pipes.