While nothing in the realm of AR tinkering is absolute, consider adding an ambidextrous magazine release to your list of parts. True, those who grip their black rifle's magwell with their nonfiring hand for support will find the mag release a mere thumb's length away, but ambidextrous-magazine releases, like those offered by Norgon and Troy Industries, afford you the ability to access the magazine release with your trigger finger, allowing all fingers of your the support hand to remain around the magwell or the fore-end.
Of the two, if I was forced to nit-pick, I'd opt for the Norgon because it has a lower profile. Regardless of the one you select, each part is drop-in easy, doesn't require any modification to you rifle and installation is identical between the two brands:
Step 1: Keeping the muzzle pointed in a safe direction, remove the magazine, pull the charging handle to the rear and make sure there is no ammunition present through visual and tactile means.
Step 2: Depress the magazine catch button, (Norgon offers an Ambi-Catch Tool for this step), which will cause the magazine catch to protrude from the left side of the rifle. Continue to hold this button in the fully depressed position throughout the installation process.
Step 3: Unscrew the existing magazine catch. Rotate the magazine catch counter-clockwise until the threads are no longer in contact with the magazine-release button.
Step 4: Remove the existing magazine catch from the receiver. You will be able to see the threaded portion of the depressed magazine-release button through the hole in the receiver.
Step 5: Holding the shaft of the Ambi-Catch perpendicular to the rifle, carefully start the threaded end of the shaft into the threaded portion of the depressed magazine-release button.
Step 6: Rotate the Ambi-Catch clockwise several full revolutions until some resistance is felt from the end of the shaft protruding through the open end of the magazine-release button. The bottom of the lever will just clear the bolt stop bosses of the receiver when the shaft is fully engaged with the magazine-release button.
Step 7: Once a sufficient number of full rotations have been made, continue to rotating the Ambi-Catch until it is in alignment with the magazine-catch slot of the receiver.
Step 8: Slowly release pressure on the magazine-release button while guiding the body of the Ambi-Catch into the magazine-catch slot of the receiver. Once the Ambi-Catch is fully seated, the end of the shaft should be flush with the top surface of the magazine-catch button. Repeat Steps 2 through 8, making one full rotation either clockwise or counter-clockwise until correct engagement is achieved. A half rotation can be made by removing the magazine-catch button from the receiver and rotating it 180 degrees.
Step 9: Function Test the Ambi-Catch with all of the magazines you will use with your AR. Test both primary and secondary methods of release. The Ambi-Catch should operate smoothly with a positive recovery.