Difference between Gracey and universal curette.. Gracey has one cutting edge while universal has two

Difference between Gracey and universal curette:

a- Section of gracey is hemicircular and in universal triangular.

b- Gracey has one cutting edge while universal has two.

c- Gracey Used for cutting in specific area while universal is in any area.

d- Universal 90 not offset, gracey 60 offset.

e- A and d

f- A, b and c.e

g- B, c and d.

(but text books say the angle of gracey is 70 degrees not 60).