This is a heavy duty center Insulator for a G5RV or ZS6BKW antenna. It follows a common design to other models I have seen but it is much thicker and reinforced.
I printed this in ASA, since this needs to have some strength and survive outdoors. I would recommend ASA for this.
I printed this as strong possible so I printed it with 20 perimeters and full top and bottom layers all the way through - essentially a solid chunk of plastic. This is probably way overkill, so print as you see fit. Something in the vicinity of 4 - 5 perimeters, 4 -5 top and bottom layers, and 40% infill would more than likely be strong enough.
The author marked this model as their own original creation.