Unfortunately I thought I had an 1800 thread count set of sheets so I told customer service that my order  for this item appeared appropriate. My reply was before I took the item out of its packaging. 
I felt the material it is very very thin (1800 thread count material is thicker). I looked at the label and it stated 1800 Series (not 1800 thread count). I have not heard of 1800 series sheets until now.  I won’t purchase sheets online anymore but only in a store so I can read the label and feel the material. The price is not adequate for this material. There is a difference between Series and Thread count. What is 1800 series?