That was stock and I replaced. In my situation they were not sufficient for my trailer. Probably not designed for the loads that they have to handle in this application. Too bad because they likely would give a better ride than otherwise.
I got my Leaf Springs from a manufacturer called Triangle based in Fontana, CA.
I had them installed with new hangers (shackles) and hardware at a place in north county San Diego that another member mentioned. They are a truck and trailer suspension shop so this was right in their wheel house. Mine are 7 leaf and they even make 8 leafs. I was told the 8 leaf would be too harsh by the installer and a couple of years later I am still great.
Etrailer does not carry them.
I would encourage you to buy from the installer so if there is an issue they will stand behind them. Let the installer size them for you too. Might cost a little more but in my opinion you don’t want to skimp on suspension, tires and brakes on a 16k lb trailer.