Cooling Fans 4 pin connecter size is not a standard size today. What size is it? adapter ?

[rlinx]

Cooling Fans (2) 4 pin connecter size is not a standard size today. What size is it? adapter ? are the pins 2.54?

Brown size is needed.

[DGroves]

5 pin fan headers are common and used on many Dell, HP,  Lenovo systems

for HP they sometimes use the 5th pin as a sense pin to determine if a optional upgraded cooling solution is installed

the other 4 pins are wired up as a normal 4 pin PWM fan connector and as such you can install a normal 4pin fan header on most HP systems 5 pin fan header

your picture shows the header with the guide slots slightly different this is done to prevent people from connecting the wrong fan header to the boards fan header(s)