A:AnswerHi Jaybird,
Thanks for the great question. The WB-300 is compatible with the SoundTouch 300 Soundbar only. Only use the following hardware to mount this product: Bose Soundbar Wall Bracket. Regards, Tony G - Bose Support
A:AnswerThank you for your question. The WB-300 Wall Bracket will not work with a Bose 321 system. This was engineered to work with the SoundTouch 300 soundbar specifically. We'd recommend reaching out to your local Bose Technical Support Team for compatible wall mounting brackets for your 321 system. Regional contact information can be found at https://global.bose.com . After selecting your region, navigate to the top-right corner of the page and select 'Support'. Then, scroll to the bottom of the page and select 'Contact Us'.
Thank you.