MultiAlerts are the ones that look like this:
https://firealarms.tv/wp-content/uploads/2016/05/maeh24m_1037_1https://cdn.thefirepanel.com/legacy/3092_6fd21bb48ddcf136c9e6c757ef70e19b.jpg
And like this:
https://4j25productionsinc.weebly.com/uploads/1/9/0/7/19078715/6693261https://cdn.thefirepanel.com/legacy/3092_6fd21bb48ddcf136c9e6c757ef70e19b.jpg
MASS is the model code of the most common product from this line, the horn/strobe. There were also stand alone horns, remote strobes (both translucent and ADA), a horn/strobe with different sounds (the MAEH), a mini-horn (including a version with a translucent strobe) and even speakers and speaker/strobes (which look very similar to the horns and horn/strobes).