Great news! 

Via Guns.com: 

Federal regulators reversed a two-year-old decision prohibiting specific use of an arm brace for AR pistols after re-addressing the issue with the company that designed the original model.

SB Tactical shared a new determination letter Tuesday that had been issued by the Bureau of Alcohol, Tobacco, Firearms and Explosives to clarify any confusion regarding shouldering the company’s “stabilizing brace.”

Shouldering a firearm equipped with a barrel less than 16 inches and an arm brace would make it an unregistered National Firearm Act item, ATF says in the letter dated March 21, adding that it continues to “stand by those conclusions.”

But “incidental, sporadic, or situational” use of a firearm equipped with an arm brace “in its original approved configuration” at or near the shoulder would not constitute a redesign nor make it an NFA item, ATF says.

Per federal law, an NFA item — a short-barreled long gun, silencer, machine gun, or any other weapon — is prohibited unless registered with the government and the owner pays registration fees.

SB Tactical owner Alex Bosco tells Guns.com the keywords here are “original approved configuration,” meaning modifications he had received in his initial determination letter in 2012.

Bosco designed the stabilizing brace to securely fit around a user’s forearm for controllable one-handed shooting. Specifications for firearms that would be ideal to use with a stabilizing brace include AR pistols with a 16-inch barrel and a fixed buffer tube or one with limited adjustable features.

The ATF letter suggests the stabilizing brace by SB Tactical creates the standard for arm braces since it was intended to be used for one-handed shooting, ideally to aid users with limited mobility.

Read more here.