I jus' found it in an earlier post.
Helps to make the AI safre you know!
Quadrential Rule, effective from transition alt to Flight Level 245 in uncontrolled airspace, is based on magnetic track NOT heading:
Track 000-089m ODD flight level
Track 090-179m ODD flight level+500'
Track 180-269m EVEN flight level
Track 270-359m EVEN flight level+500'
Above FL 245 the Semi-Circular rule applies:
Track 000-179m FL 250, 270, 290 then every 4000'
track 180-359m FL 260, 280, 310 then every 4000'