On the zoo med plants I use, there is a reinforcement wire running through the main part of the plant. Most times it feels to be a little sharp. It's located roughly at the part where the vines branch out. It's covered/ molded over to look like the rest of the vine. And sits "at top" where you would insert the plant into the suction cup. It can be difficult to notice. I usally run a metal file over it to smooth and remove any potentially sharp edges. If anyone is truly interested I'll post a picture.