The tool is designed to measure the oil level of transmission.

Full length: 920mm

This dip stick is put into the dipstick tube until it hits the pan and you take the reading from there.
Engine must be hot and running when taking this reading.
As a general guide the fluid level should be between the 8 and 9 markings when hot. 

Models: 722.7 / 722.8 / 176.5 (168 A Class) 

OEM: 168 589 01 21 00 / 168589012100