ABC/R (Augmented Bolt Catch/Release) with its angled and larger top paddle and lower paddle with increased surface area, is purpose designed for use with AR15/M16 receivers equipped with ambidextrous magazine releases. Specifically, it is designed to address the difficulty with accessing the factory bolt catch's lower paddle with an ambidextrous magazine catch, such as Norgon's Ambi-Catch, on the receiver.
The lower paddle protrudes further, and is angled at 10 degree to give it even more surface area. These measures put the lower paddle and Ambi-Catch's paddle on different vertical planes. The angled paddle makes it easier for the palm or thumb to access.
The notch immediately above the ABC/R’s lower paddle is meant to provide tactile feedback to indicate the beginning of the lower paddle.
The "butterfly" lower paddle's horizontal extension increases the lower paddle's surface area, but stops short of reaching the bottom of the bolt catch in order to create a stand off distance between the extension and an ambidextrous magazine catch's lever. The butterfly lower paddle has increased surface area, and doesn't interfere with an ambi mag catch's lever.
For 2020 ABC/R version 3 consists of the following changes:
* Ledge on top of the upper paddle, and bottom of the lower paddle to increase traction.
* Upper paddle options: FB (forward biased), standard (centered upper paddle), RB (rearward biased).
* "Butterfly" lower paddle with increased surface area, while maintaining a healthy standoff distance from an ambidextrous magazine catch's lever.
* Slightly lengthened magazine follower trip. Do note that the longer magazine follower trip is designed to make the bolt hold open after the last shot more reliable with more magazine varieties, but not meant to be a fix for out of spec receivers. We can lengthen it to a degree before running into unintended consequences by making the trip too long.
Machined from billet 8620 alloy steel and heat treated with DLC finish. The ABC/R v3 is proudly designed and made in the USA. Starting from June 15, 2018, bolt catch roll pin, plunger and spring are included.
NOTE:
* ABC/R is designed and made for TDP spec AR15/M16 in 5.56mm. Due to the wildly varying configurations of PCCs it is not advisable to use ABC/R on 9mm carbines. Do not use ABC/R on PCCs.
*ABC/R v3 with forward biased upper paddle may need minor fitting to work with BCM Mk2 upper receivers.
Solid Addition 
