Summary

These inserts will fit in those basic driveway reflectors available at any hardware store. Just pop out the reflector and pop in the insert.
The inserts are designed to hold the 2" Daisy Shatterblast Discs. A rubber band across the back will keep the discs in place
Stick them in the ground or make a spinning target

This thing was made with Tinkercad. Edit it online https://www.tinkercad.com/things/gPsyQUNv3Yf