Comparison : Item # 9S1212L401, 12V Ribbed Silent Square DC Fan (w. Pulse Sensor)
Item # 9S1212M401, 12V Ribbed Silent Square DC Fan (w. Pulse Sensor)
Item # 9S1212P4F011, 12V Ribless Silent Square DC Fan (w. PWM Control & Pulse Sensor)
Item # 9S1224M401, 24V Ribbed Silent Square DC Fan (w. Pulse Sensor)
Item # 9S0612F4011, 12V Ribless Silent Square DC Fan (w. Pulse Sensor)
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