not kenko ones, got them today, they look exactly the same as yours. the casing is plastic and not metal as i thought. It keeps the weight down i guess. the mounts, bayonets etc are all metal. Not sure if yours in the link are just coated metal as mine are stainless steel by the looks of it.
Only had a little play at the moment with my 3 primes, not sure which i would use with the tubes. However im not looking for 1:1, just looking to have a ring handy in the bag if i go out for a walk etc...