General data on commonly used parameters of roughness

Mean arithmetic deviation of profile Ra (ISO 4287, DIN 4768).
Mean arithmetic deviation of the Ra profile is the average value of the absolute value of the profile deflection within the basic length I.

Maximum cavity depth on the Rmax profile (DIN 4768).
Maximum depth of the cavity on the Rmax profile is the largest of the existing individual depths of the Zi roughness at the common measuring length lm. In accordance with ISO 4288 and DIN 4287 - Part 1, this parameter is also called Ry max.

Average roughness depth Rz DIN (DIN 4768). The
Average depth of roughness Rz is the arithmetic mean of the individual depths of the roughness in a consecutive sample of lengths le. In accordance with ISO 4287 and DIN 4762, the Rz DIN parameter is also called Ry5.
Rz is differently called in DIN 4768 and ISO 4287, this parameter is also called Rz DIN and Rz ISO.
When the parameter Rz is measured in accordance with the DIN standard, in general it is assumed that the final ISO value also applies, if Rz DIN does not exceed Rz ISO.