Similar to the boom mount, this antenna mount is much stronger to support the extra weight of a heavy riser. 
 
The lower mount has thicker walls, a thicker floor, denser internal fill, two bolts instead of one, and a padded base for the riser to sit in distributing the weight evenly. 
 
Made with highly durable and weather/UV-resistant ASA filament and stainless steel hardware integrated into the print.