Lenox Tools has the best product for hole saws.  This will last a lifetime.  I do not know why they call this an electricians kit because it has sizes up to 4 inches which is good for the majority of plumbing needs.  High quality! Great price.  Well worth it! You may have to eventually replace a saw blade if you use it on metal or tile, but for wood they do not get dull. Lenox has engineered this for useability.  Easy change out and plug removal.  This is what the professionals use at almost twice the cost.