Five items assess the strength of a person's self-categorisation as a member of a community organised around a shared brand, including attachment, shared purpose, and belonging.
Algesheimer, R., Dholakia, U. M., & Herrmann, A. (2005). The social influence of brand community: Evidence from European car clubs. Journal of Marketing, 69(3), 19–34.
Free access to 2023+ psychometric scales at PsychScales