The NFL and NFL Players Association have added 11 helmets to their joint list of approved equipment for 2019 while eliminating a grace period for other models that have fallen short in laboratory testing, engineers and executives representing both groups said Friday.

By the end of last season, 32 players, including New England Patriots quarterback Tom Brady, were wearing helmets that are now banned.

Jeff Miller, the NFL's executive vice president for health and safety initiatives, said it is "eminently doable" to convert them to approved equipment.

Each team's equipment manager has been instructed to remove all banned helmets, which are listed on a poster distributed to teams Friday. If a team is found to have known about a player wearing a banned helmet, or to have facilitated the use of one, it will be subject to league discipline, Miller said on a conference call with reporters.

The NFL and NFLPA have been testing helmets since 2015, but they agreed for the first time last year to prohibit lower-performing models. Six were banned immediately and four others, including the one often used by Brady, were allowed to be worn for one more year.

There were no additions to the list of banned helmets for 2019. Of the 11 models tested this spring, nine were new to the market, one was tweaked significantly and another had been overlooked in 2018, according to Dr. Kristy Arbogast, the NFLPA's engineering consultant.

Six of the new helmets were ranked among the top 10 on the 2019 poster. For the third consecutive year, the VICIS Zero1 helmet landed atop the list, followed by the Schutt F7 LTD and the Riddell SpeedFlex Precision Diamond.

"One of the most exciting things is seeing how our years of testing protocol is really driving innovation," Arbogast said. "You can see when you see the poster that many of the new helmets that are being introduced to the market are top performers. And so I think through the perspective of the players, it's phenomenal that we are driving innovation and we are driving design to release products that perform better on the field."

The Riddell VSR-4 helmet, introduced in 1993, can no longer be used in the NFL. Michael Dwyer/AP Photo

About 50 percent of players moved to a better-performing helmet in 2018, according to statistics released by the NFL. By Week 17 of last season, 74 percent of players used a helmet that ranked in the top category. The NFL will send a list to teams of the 32 players who were still wearing underperforming helmets in 2018 to help facilitate upgrades.

Arbogast said players who objected to the change mostly said they preferred the fit, comfort and look of their old helmets. Dr. Jeff Crandall, chairman of the NFL's engineering committee, said several of the models added to this year's list are upgraded versions of those helmets.

"One of the things that prevented some players from moving," Crandall said, "might have been about comfort or fit or aesthetics of the helmet, not necessarily the safety. But there is a wide number of [approved helmets] that are comparable in the aesthetics now. We're optimistic that this will lead to a migration of folks."

The helmet testing is conducted in a lab at Biokinetics Inc. in Canada. According to Crandall, crash test dummies wearing each helmet are outfitted with sensors and put through impacts of eight locations at three speeds each. The tests focus on linear accelerations, rotational accelerations and velocity, he said, and lead to a performance metric that "characterizes the ability of the helmet to manage the forces of impact."