What do you mean by M16x20 by 25 designation for Tapped holes?

The designation M16x20 by 25 for tapped holes indicates a metric thread size. The "M16" specifies a nominal diameter of 16 mm and a thread pitch of 2.0 mm, while "20" refers to the depth of the hole in mm, indicating that the hole should be 20 mm deep. The "25" typically denotes the length of the threaded portion, suggesting that the hole should accommodate a screw or bolt that is 25 mm long. Overall, this designation helps ensure proper fitting and assembly in mechanical applications.