Ben, better yet IMO, are Sparky's.
They are molded rubber, waterproof and cheap. I use them on all my offroad bikes also.
You can find them at most motorcycle shops.
They fit so tight that vibration won't get them off and it makes them watertite.
I just got the NGK's in the mail from Spruce, when I get a call from a buddy who has 4 of the rotax ones...I ask him whats the dfference and he says "beats me ...about 13 bucks..." and he works for the gyroplane company!
So I was wondering if anyone else is using the NGK ones...
I already got them installed.
only thing I don't like is there isnt a flat top that was on the rotax ones. I had used a sharpie to number them 1-4. I guess I will use some tiny zip ties to number these.
Let you know tomorrow how the radio sounds with them.