6mm and 16mm threads

I have the 6mm lens at the moment for the pi HQ cam, but will be getting the 16mm soon.
Can someone confirm what the thread is on the end of both these lenses? I’m not meaning the end that screws into the camera, the other end.
Basically, i am wanting to buy some filters to place over the lens but can’t work out what size thread is on the 6mm and also need to know for the 16mm so i can get an adaptor to use the filters on both.