Block crosses and tees, flanged or studded, in accordance with API Spec. 6A are available. They are forged or casted from high performance alloy steel, robust, and high cost performance.
Studded crosses and tees, flanged crosses and tees are widely used for choke manifolds, kill manifolds, mud manifolds and christmas trees.
Cross-over Spools (Cross-over Casing Spools or Crossover Tubing Spools), in accordance with API 6A, suspend and seal around a string of casing or tubing, the spool can contain a restricted-area sealing means at or near the face of the lower connector, permitting a pressure rating greater than the pressure rating of the lower connector in the section above the restricted-area sealing means.
Spacer Spools, in accordance with API 6A, have end connectors of the same size, rated working pressure and design. Spacer spools are wellhead sections which have no provision for suspension of tubular members and which may have no provision for sealing of tubular members.