You do not want the sealer 4" thick. That is a huge waste of money.
Proper ratio is 1/2 as deep as the width...
On an 1/8" width, you can't do a 1/16" depth, nor is under 1/4" deep recommended.
I went the depth of the tool I recommended, which was about 1/2"
4 years later, not one of them has...