I recommend it because it can avoid losing your lens cap,
Indeed, if you have an SLR and one goal, just to have a simple strap linking the lens cap with the strap of the camera / camera. (Because the objective will remain fixed to the casing)
Now, if you have multiple goals, you need to lose that precious cache, plug door is perfect because it allows easy switcher your goals without losing your cap!
I confirm the comptatibilité with 18-105 Nikkor 67mm diameter.
I recommend, especially at this price, it costs less than ordering a new plug!