Swivel Housing Filler plug size

Morning,
My 2005 TD5 has one filler plug in the front swivel housings, which I need to undo and top up with one-shot grease, but I wanted to check with you guys because I keep reading that the filler plug is a 1/2 female square plug, but is there a special tool for it, or do I just shove in a 1/2 inch ratchet head from my tool set ?
and are there other sizes it could be because the female filler plug looks smaller than 1/2 inch.
cheers

use a 13mm spanner or a 6 inch 1/2 inch extension and a spanner on that

The spanner won't work because it's a female recessed plug, not male.
So you are saying just shove a 1/2 inch socket into the hole.

Justin-JP said:

The spanner won't work because it's a female recessed plug, not male.
So you are saying just shove a 1/2 inch socket into the hole.

Click to expand...

Yep, 1/2” socket driver.

I'm sure mine is 3/8" female on the plug, just use an extension bar in the ratchet. 2001 TD5.....