This is an adapter that fits a 40v Hyper Tough 16" lawn mower, and allows you to mount a replacement blade I bought which is meant for a Greenworks mower. You will also need a washer to hold the blade on, greater than 22mm diameter with 8mm hole.
I printed this in PETG.
Original mower models: HT21-401-003-01, HT10-401-003-01, HT22-401-03-06
Replacement blade mower models: 25322, 25242, 25142
Here is the blade I bought: https://www.amazon.com/dp/B00PBYZEJM
The author marked this model as their own original creation. Imported from Thingiverse.