Normally, I listen to reviewers on this site for advice. If there are a lot of 1 star ratings, I tend to raise an eyebrow after filtering out ones where people may or may not know what they're doing. This is one purchase I wish I listened to the negative reviews on here.
Plastic. Why use a plastic adapter for a filtration system? After first installing, it worked like a charm...until the first time I tried to fill a pitcher with it. Barely grazing this device will cause it to fall off, and spray water everywhere. This happened about 6 times, and then I went and got some teflon tape to wrap around the adapter. This worked for a little while, however, it would still leak a little through the threads. Then, it fell off again after the slightest bump of a hand (or maybe a feather fell on it, it's all the same with this piece of junk).
I will be taking this back to Target tomorrow...what a waste of time and money.
The filter pitcher option will probably be my next buy. I had one a while ago, and it worked pretty good. As for this, I recommend to stay away from this, unless you are willing to bond this thing permanently to your faucet.