Description Aura AST-1B-4 (regular, non-pro) Frequency Range: 20-100 Hz Effective Impedance: 4 Ohms Resonance Frequency (fo): 42 Hz Force: 10 LBf (44.5 N) at 25 W Peak Force: 20 Lbf (89N) at 50W Continuous Rated Power: Nominal 25 W RMS Max power: 50W RMS Resonant Spring: 2 molded nylon/plastic spiders with 3 spokes Voice Coil: single layer, 3" diameter, the voice coil is fixed and the magnet is the moving mass in the middle. Xmax ~= Xsus = 1/8" Moving Mass: magnet cylinder 3" diameter by 1" height. Size: 4.75" (diameter), 2.35" (height) Frame Size: 5.4"w x 2.2"h Weight: 2.5 lbs Magnet Type: Ceramic **** (That's 2 shakers in 1 box) ****