What is the principals scale as per 6th pay commission?

The 6th Pay Commission didn't use a single "Principal Scale." Instead, it defined various pay scales for different levels and cadres of government employees in India. There were numerous scales, each with its own grade pay and pay band. There wasn't one overarching "Principal Scale" to encompass all of them. To find a specific scale, you'd need to know the employee's position and cadre.