Well, until there are major advances in plastics technology, no "realistic" dildo is all that realistic. Dildos are not warm like real cocks, the skin does not slide up and down the penis shaft, and the balls don't move inside the scrotum or slap against your ass.
Some have softer material in the dick head that makes the initial penetration easier. But at the same time I prefer a firmer dick head that is wider than the penis shaft that massages the anal muscles near the entrance of my ass.
So in the end, I go for the look - a cock that turns me on. I've always liked the Doc J "realistic cock." Big, thick, and fills my ass just right.
ference dong is just a bit too much work, though it is fun when I get it in. This one just goes in and hit the right spots. They also come colored like a Hispanic person or a Black person and in a variety of sizes from 4 to 9 or ten inches and either straight or curved. I like the curved. The head is large enough to feel great going in but small enough to go in without too much stretching.
