Appears to be an original spec Fujifilm lens cover. Fitted perfectly. Bit expensive at £11.49 (free postage) but then that's the price of photography (at the moment...)
A lens cap is always a good idea. Unfortunately, with this one you have to be very careful not to loose it.
The grip on the front of the lens is not as tight as it might be, in which case it would have been a good idea if Fuji had also added a restraining cord to keep the cap attached to the camera strap even when it happens to fall off the front of the lens.
So, buy the cap, but make your own cord to prevent it from being lost.
I lost the one that came with the lens, so i have been through the process of having to replace it.
That is why I bought this one.