upright mushrooms

[3GE Components]

The reason they are offset is to align the top and bottom pivots with the axle centre line better, If you draw an imaginary line through the Sierra upright you will see that if the mushroom insert is concentric it will miss the centre line of the axle, requiring more effort to self centre.

The reason some suppliers mushrooms are concentric is cost, put plain and simple they are cheaper to make.

Hope that all make sense

Kind regards

John