Maybe a nice-to-have, but...I got one of these in black and put it on my 7.62x39 AR. Well, it fits and looks okay [you have to remove the trigger guard to install it]. It gives you two fingers of gripping surface on the front of the mag well, and will possibly protect your trigger finger inside the guard...but nothing a pair of gloves won't do. I like Ergo products and this seems to be good quality, but I'm really not convinced of its utility.
Ergo Grip 4965 Never Quit Magwell Grip AR-15/M16/M4
The ERGO Never Quit Magwell Grip reconfigures the squared shape of the AR/M4 magazine well.
This fits AR-15/M-16 lower receivers with a removable trigger guard.
Note: It does not fit AR-10 large frame receivers or receivers with a permanently attached trigger guard.