https://aerocooler.com/top-motor-df124028bu-pwmg-40x40x28mm-dual-ball-bearing-pwm-fan-4pin-pwm/
Top Motor DF124028BU-PWMG 40x40x28mm Dual Ball bearing PWM Fan, 4PIN PWM - AeroCooler
Top Motor DF124028BU-PWMG 40x40x28mm Dual Ball bearing PWM Fan, 4PIN PWM
dual ball
https://aerocooler.com/productimage.php?product_id=5057
Top Motor DF124028BU-3G 40x40x28mm Dual Ball bearing Fan, 3Pin
dual balltopmotorbearingfan