HHO High Frequency PWM DC Motor Speed Controller 30A [Box / Fan Ready to use] 100% Tracking Number Require Power Supply 12 -30 VDC / 30A Max. Load with fuse protection 2 Ranges of Frequency Adjustable 1. Connect Jumper for 1.2kHz to 6.4kHz 2. Remove Jumper for 12kHz to 64 kHz Build in soft start fuction 2 second, can be increase to 10s by changing the soft-start capacitor ABS Box size : 11cm x 15cm x 6cm(Height) / 12V FAN size :6cm Diameter