Space saving mounting solution for subs and mains The JBLPOLE-MA features an amazing height adjustment collar that features an ergonomic "Z" knob that provides comfortable adjustment. The strongest fitting made, the height adjustment collar prevents overtightening and breakage issues associated with all plastic designs. Plus, the die-cast zinc fitting is 30x stronger than ABS or Nylon plastic used by the competition. Fits all JBL EON, PRX, STX, VRX and SRX818 Subwoofers.