This is the Lima Six ar-15 nutsack adapter. This goes into a tradition ar-15 magwell, locks securely into place, and allows the use of the nutsack at the correct feed angle. These are solid and good to go. They aren’t breaking on you. 
 
These products are all made right here in The USA!
 
Please note that due to the nature of 3D printing, minor imperfections may be present. However, we stand behind the quality of our products—if it breaks, we’ll send you a replacement, no questions asked. I