From the MEElectronics Facebook page: WEEKEND SALE: Buy a M11+/M11P+, M6/M6P, M9/M9P on sale and get a FREE M2P hands free to leave in your car or wherever you use your compatible phone! Sales prices: M11+/M11P+ is $20 off, M6/M6P is $10 off, M9/M9P is $5 off - Up to a $40 value so don't miss out! https://www.meelec.com/

Note that the Facebook post says the P versions are also on sale and you can get a free M2P, but the site banner does not. It does seem to work with the M11P+, M6P, and M9P.