Perhaps a half inch.
No. This is for a 2 3/8" post as it states in the description. It would be too big for a 1 5/8 post.
Tariffs on imported aluminum.
Unless I am totally wrong I would imagine you could just use a spray can of black Rustoleum on it. But to be on the safe side make sure it will go on and cover aluminum alright.
mine measure ~2.55" and the bead is ~2.71"
It fits over the end
The '2' is inches. The cap fits Posts whose outside diameter is two and three eighth inches (2-3/8).