Firm nipple clamps of good quality, these are Rimba clamps. The clamps are made of metal with a chain in between. Here you can also attach your own material, such as ropes, other chains or weights. You can also use the chain to (gently) put on.
Suitable for beginners and advanced, the clamps are adjustable with a screw. The tighter you turn the screw, the looser the clamp. You can make it as exciting as you want.