No, it is not. Over time chemicals in the plastic may be released into the water which are not safe.
I wish I still had this piece to measure the center non-threaded bit for you, it's got to be 1/4 " or less. I screwed one side into a sprinkler head and the other side into a PVC elbow, they might as well have been touching.This is basically a female to male converter, good for keeping things as close together as possible.
About 1 1/2"
Close means it is the shortest it can be, just the threads from each end with no unthreaded pipe in between, or very little. the two fittings you are connecting will be close upon each other.