THIS POST IS FOR INFORMATIONAL PURPOSES ONLY
It seems like there is a bit of misinformation in terms of fan shroud designs for the E3D hot-end heatsinks. I found this out while I was searching for compatible fan shrouds for my E3D heatsink.
AFAIK, most people think the differences between the 25mm diameter heatsink and the 22.3mm diameter heatsink are down to whether it's a clone or original.
As shown in the screenshot of the E3D website, the difference between these models is actually whether it's a V5 compatible heatsink, or a V6 compatible.
The V5 heatsink is longer, uses M6 threads on the bottom to connect to the heatbreak and heater cardridge and has a wider diameter of 25mm. The V6 is shorter, uses M7 threads on the bottom and has a narrower diameter of 22.3mm.
See this link for the original page where I got this information from: https://e3d-online.com/v6-heatsink-1-75mm-universal-with-bowden-fitting
Happy designing and printing your fan shrouds and other accessories!
PS: I've attached a 1mm^3 cube to be able to upload this. This serves NO further purpose!