Steel and elastomer assembly that has a central through-passage equal to or greater in diameter than the riser bore and that may be positioned in the riser string to reduce local bending stresses.
The Mazatec people are an indigenous people who inhabit an area known as the Sierra Mazateca in the state of Oaxaca in southern Mexico, as well as some communities in the adjacent states of Puebla and Veracruz.
The Toltec formed a warrior aristocracy that gained ascendancy in the Valley of Mexico c.AD 900 after the fall of Teotihuacan. TeotihuacÃ¡n their early history is obscure but they seem to have had ancient links with The mixtec and The. Zapotec their capital Was (tollan TollÃ¡n). see tula