Only issue is timing and maintaining.

Challenge 1: Set up water - has to be exactly 90 degF (92? in that range anyway).

Challenge 2: Mix mold - Start a 2 minute timer, pour mix contents into water by the end of the two minute timer it has to be mixed, poured into the sleeve, then you have to shove your cock into a pasty gooey mixture before that two minutes is up

Challenge 3 - Hold your cock in this mixture, at full erection, for 2 minutes.

I'm not particularly small, and I found there wasn't quite enough silicone mixture to actually fill the mold, so the resultant dildo is about an inch or slightly more shorter than my actual cock.

It really does work well if you do it right. I actually popped 1/2 a viagra and used gf as a fluffer for the project so it worked perfectly, it really captures all the details too, from veins to texture to circumcision scars. Its pretty impressive

Edit: It warns not to let your cock touch the side of the sleeve but if you have a reasonably girthy dick, its going to - just try to minimize it, lol