I had the red 3 3/8" on a 50cc engine.
They are very very light weight.
The hardest thing I had was making the prop cut outs to match the prop hub mounting hole ( in the backplate ) to match the four little srews that hold the spinner onto the backing plate.
Getting all three in the right spot and keeping the prop cut as small as posible is a real pain.
I lost one of the small spinner bolts and the rest of it ended up cracking.
It is nice quality, it could have just been me and the way I did it. [&o]
I like and am sticking to spinners with the single center bolt.
No alignment problems, one bolt, easy to use.