Take a look at Figure 4-6 (page 4-21 in my version) in AC 43.13
The second row down shows how a correct set should sit on the rivet.
The size of the set should be stamped on the rim of the set.
But, I agree with the others. Looks like an AD3 set on an AD4 rivet.
N164WM RV-6A Slider/O-360/FP Sold 4/2022
N184WM (RV-8) Flying. Titan IOX-370/ CS/G3X
N184P reserved (RV-8QB) Empennage kit and QB wings in the shop