An ordinary clothes peg with an extra C ring to give it more spring power on griping(v1.1). It works without the ring (v1.0) but the grip is kind of weaker like all other print in place peg. I print with Ender v3 se, with horizontal expansion set to -0.02. If the mouth sticked together, you can open it with a plier open in the middle void. In my case, usually just the first layer stick together.