From Shires:

#7: Modified two piece construction made to combine the best playing characteristics of both one piece and two piece bells. Soldered bead favors pointed articulations and centered sound, more stability to the sustain of tone.

Y: Yellow brass—70% copper, 30% zinc—clear, pure sound with strong fundamental, keeps a very consistent tone color and overtone structure throughout the range of dynamics

M: Medium weight:—slightly lighter than standard weight, characteristics between standard and LW

Standard size (8.5”) and taper (TI)