I measured my Classic 3 with Classic 33 arm when I ordered my MINTLP. it came out to 258mm, effective length adopted is 273mm. If you measure yours ensure you measure it from the center of the spindle and ensure the ruler is level, otherwise the length will increase by 0.2mm because of the height difference between the spindle and pivot. There are a number of different answers out there if you do a search. Best way is to measure yours.
