In the nearly 17 months since then-Oakland Athletics pitcher Brandon McCarthy was struck in the head by a line drive and suffered life-threatening brain injuries, Major League Baseball says it has received and tested numerous prototypes from different vendors for padded caps to provide some head protection against high-speed shots off the bat.

On Tuesday morning, MLB informed its 30 teams that it has approved such a product for the first time, after consultation with the players' association, according to Dan Halem, MLB executive vice president for labor relations.

"We're excited to have a product that meets our safety criteria," Halem told "Outside the Lines," adding that baseball will continue its efforts to come up with more options. "MLB is committed to working with manufacturers to develop products that offer maximum protection to our players, and we're not stopping at all."

Halem and MLB senior counsel for labor relations Patrick Houlihan said the threshold for approval was that the cap had to provide protection, at 83 miles per hour, below the National Operating Committee on Standards for Athletic Equipment standard severity index of 1,200. Severity indexes higher than 1,200 are considered high-risk for skull fractures and traumatic brain injuries. An MLB-commissioned study determined that 83 mph was the average speed of a line drive when it reaches the area of the pitching mound.

The newly approved caps, manufactured by 4Licensing Corporation subsidiary isoBlox, will be made available to pitchers for spring training next month. Their use is optional.

The company says the caps are a little more than a half-inch thicker in the front and an inch thicker on the sides -- near the temples -- than standard caps, and afford protection for frontal impact locations against line drives of up to 90 mph and for side impact locations at up to 85 mph. The soft padding, isoBlox says, is made of "plastic injection molded polymers combined with a foam substrate" and is designed to diffuse energy upon impact through a combination of dispersion and absorption techniques.

"What we've given [pitchers] is a product with protection they've never had before," said 4Licensing chief executive officer Bruce Foster. "It changes the game for them."

In addition to the added thickness, the padding adds seven ounces to the weight of a cap, which currently weighs three to four ounces, said Foster. The padding is to be sent to New Era to sew into MLB's official custom-fitted caps.

"I think players who've been hit by ferocious comebackers will probably be early adopters," Foster said. The new cap, he said, won't interfere with a pitcher's comfort or motion.

"Outside the Lines" research has found that 12 pitchers have been hit in the head by line drives in the past six seasons, including five pitchers during a five-month stretch of action in 2012 and 2013. Among them was Toronto Blue Jays lefty J.A. Happ, who suffered a fractured skull and also sprained knee ligaments on his fall after he was struck in the left ear on May 7, 2013.