A red circle (centre at Y) has been drawn of equal radius to the Sarsen Circle. ( aX = ZY)

Where it meets the phase 3 axis line at r a further circle has been drawn of radius Xr which equals the R Ring radius at Stonehenge.

Where the red circle meets the phase 3 axis line at A a further circle has been drawn of radius XA which maps out the position of the Aubrey Holes.

GEOMETRIC CONCLUSION

The distance from the Y ring holes to the Aubrey Circle , is the same distance as the Sarsen Circle radius.