What is this for?

[bully]

I realise this is a fisheye converter but what for?

The rear of it is 35mm diameter and has a screw thread.

It was in the rucksack my SLR was in but it isn't an SLR fit.

I want to get rid of it and have looked on the net but not much came up.

 

[Ay Ay Ron]

Looks like one I had for an old video camera.

 

[Laura]

you get an adaptor ring and fit it to the end of your lens, ive got one, they are only cheap £45 ish from memory.