I bought these because I picked up a VZ.24 Mauser and figured that at a bare minimum I should have a trigger lock.  The fit is not perfect, but it locks on so that you would need to be determined to hit the trigger (you'd need a thin rod or other tool to push into the gap), and you can't get enough of play to trip the trigger.  With ammo stored in a separate location and no children at the house I figure I've covered due diligence.  They do the job, and fit well enough on my pellet gun that I can throw it on there if I feel the need.