Depending on the experience of use (technology), the glass fiber was broken at the base on the first day it was used. It is damaged too much unlike the hammer used until now. Damage was not only applied but also floating over the whole glass fiber and it got peeled off. Does the glass fiber have insufficient viscosity compared to other comparable products, or is it too hard? Products sold with thicker protective rubber were sold under the head of the hammer at the same amount in other home centers. I think that it would be good if there was improvement of protective rubber under the hammer.