I needed to replace the bathroom caulks since the old ones were getting moldy. I have a caulk gun as well but I like this one more convenient (Easy to use and offers more precision). If you carefully remove all of the pre-existing caulk and let it dry for 24 hours before exposing it to water, then you are good to go. I have no previous caulking experience and I am a miserable DIY guy. If I can do this then every one can do. It has been over a month and I noticed no leak or cracking. Will update the review if it happens but (touch wood) so far so good.