It seems like you're asking for a short description of a product, "PH ADJUSTER 401, 20L MK." Based on the name, it appears to be a type of pH adjuster or pH regulator, likely in a 20-liter container, possibly used in various industrial, agricultural, or water treatment applications.
A short description might be:
"PH ADJUSTER 401, 20L MK: A liquid solution designed to adjust and stabilize pH levels in water or soil, ensuring optimal conditions for various applications. Available in a 20-liter container for convenient use in larger scale operations."
If you need more details or have specific requirements for the description, feel free to provide additional context!