I do not profess to be microbiologist, I am an engineer who fixes things most have no idea are broken. Also, my information on the size came from a renown microbiologist. The decimal or number could have been a typo. Regardless, I do not consider any of this a contest of any kind. Nor am I here to sell or assuage. I am here to enlighten with 2 basic ideas to consider. 1-Would you rather have a shower head designed to be opened and dry every day and clean at will with the flip of a latch or, 2- A Shower Head that you cannot verify what is inside, always wet and use the Dr. Falkingham method of fully removing the shower head once a month and submersing it in undiluted bleach. Then reinstalling.