Was this a setup you machined? I've been considering making an ER32 or 40 spindle setup like a taig spindle for doing repair work.
The picture is just a phenolic ferrule and a jump tip that was turned.
The ER40 set up is something I turned up to fit the existing 40mm id bearings that are in common Taig type headstocks.
I use the Rego-Fix brand ER40 collet nuts and collets, but have brought some cheaper collets to see what they were like.
In this set up is the 25mm collet with a wood sleeve to suite the shaft taper.
The back thread is the **x 32tpi that suite the Taig type 3 and 4 jaw chucks.
I think the through hole on mine is Ø31mm
I was going to make it ER32 but chose the 40 for the larger through size and the slightly larger nut diameter, gives enough diameter to be tight enough without having to use a spanner to tighten it up.
If you want any more info then feel free to PM your email and I can send you that info to email directly.
Neil