The "Plastic Fantastic is a good enough optic but the build quality is about as bad as it gets. Mine still works after three years of light use, but it is as noisy as it gets, it wobbles a lot, it's built from the cheapest plastic you ever seen, and it feels like a toy!
My Vivitar version of the lens at one time had a giant hair stuck in it that made it useless beyond f11, but the hair seemed to disappear over time so it is now functional again. Dealing with the 1:1 attachment
is not convenient and macro shooting would be much smoother if you could use the
full range of the lens without needing to add and remove the diopter. This older lens design
may to lead to easier blowouts than most of my other lenses on digital, and of the 35 or so A-mount lenses I have owned, this lens is the worst built of all of them. However, the glass inside this lens is far from the worst, and the lens can produce some very good results for most folks. Do not use this lens in a dusty, dirty environments, or you will be sorry...If
you are in need of a Macro lens on the cheap then the Plastic Fantastic (Vivitar,
Cosina,) may be a useful purchase for you.