1- Pressure rating of BOP (5k psi , 10k psi, 15k psi)
2- Size (Inner Bore diameter of the BOP) , (7 1/16″, 11″, 13 5/8″, 18 3/4″)
3- Code for BOP stack components from the bottom to the top
(A: Annular, R: single ram type, Rd: Double ram type, S: Drilling Spool)
Double ram means two independent ram cavities stacked vertically within the same body.
In the attached photo:
BOP: 10k – 13 5/8″- RRdA