A centralizer having a plurality of collapsible bows interconnecting a first collar and a second collar, with the centralizer disposed on a tubular with a stop collar, and an attachable retainer(s) of the centralizer blocking passage of the stop collar therethrough. The bows may have a yield strength of at least about 200,000 psi. Outer surface of the bows may have a coefficient of friction equal or less than about 0.02. Maximum radial thickness of centralizer when the plurality of collapsible bows is fully collapsed may be equal to or less than 3/16″. Centralizer may be rotatable relative to tubular. Centralizer having a split tubular body forming first and second collars connected by collapsible bows and a retainer to retain the split tubular body on the tubular, and the retainer, the first collar and/or the second collar providing a recess therein to receive a stop collar of the tubular.