Yeah, to me me these are a second rate option.
First rate options:
- extension tubes
- macro lenses (lenses, not filters)
Extension tubes come in sets of three different lengths. They're used one at a time or stacked, between the lens and the camera body - so they literally extend the lens away from the sensor. This dramatically reduces the focal length (and the depth of field). They can be used with most lenses (above 50mm) but are better with primes than with zooms. They're fairly affordable. (see Clive's link above)
The more expensive, but best option, is a dedicated macro lens. The Sony brand lenses are the 50mm macro and 100/2.8 macro. Minolta used to also do a 200/4 Macro, but Sony haven't re-released that one (yet...)
Lots of zooms will have the word macro written on them - ignore that, it's marketing. You want a proper macro lens (1:1 magnification).
There are cheaper third party options - the Tamron 90mm macro is very well thought of. Sigma also have a couple, but I'd stick to Sony/Minolta or Tamron