1 1/4 in
GF 6380294 Anodeless Riser With PE2406/PE2708 Pipe 1-1/4 in Nominal, MNPT x IPS
A nice touch here is the zinc coated exterior that adds a bit of weight and solidity.
SB1 Threaded Tank Coupling (Standard) 1-1/4" FNPT Sandblast Cast Iron SB1CI
I chose this unbranded model because it fits my needs without the markup.