Wide receiver Antonio Brown is not relenting in his efforts to get his favored helmet approved. (Christian Petersen/Getty Images)

Oakland Raiders wide receiver Antonio Brown is not giving up in his attempt to wear his preferred helmet model.

Brown filed a second grievance against the NFL over the matter Monday night, according to a person familiar with the case. It was not immediately clear when it would be heard and resolved.

Brown lost his previous grievance, in which he was trying to force the league to allow him to wear a helmet model discontinued by the manufacturer. Brown was one of 32 NFL players informed last season they would have to switch this year to a helmet model approved by the league and the NFL Players Association under a joint program by which helmets are evaluated on their performances in laboratory testing.

Brown’s helmet model was not originally tested because it was no longer being made by its manufacturer, Schutt. Brown’s particular helmet was more than 10 years old and therefore was not certified by the national governing body and not approved for use by the NFL.

After losing the previous grievance, Brown and his representatives located a helmet of Brown’s preferred model, the Schutt AiR Advantage, made fewer than 10 years ago, believing that would allow Brown to wear it this season. The league then put that helmet model through testing and determined it is not approved for use. Brown’s grievance contends he should be permitted to wear the newer version of the Schutt AiR Advantage because he has not been given the one-year grace period for wearing his non-approved helmet that other players were given last season.

Brown reportedly rejoined the Raiders on Monday after the team’s general manager, Mike Mayock, told reporters Sunday it was time for the seven-time Pro Bowl selection “to be all-in or all-out.” The Raiders obtained Brown in an offseason trade with the Pittsburgh Steelers. He has missed time in training camp because of injuries to his feet reportedly caused when he failed to wear proper footwear during a cryotherapy treatment.

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