We've found Forcefield Armor inserts work well with our jackets.
Back inserts are the small shape B pad. The Forcefield small Shape B back inserts fit the back armor pockets (16.5"x13.5"), and the elbow and shoulder Limb inserts are Type B. We recommend four shoulder pieces to use in both the arm and shoulder pockets (9"x7").
The four jackets we have with armor provisional pockets:
NOTE:
T-Pro Armor may not fit all shoulder pockets unless it is trimmed to fit. Some shoulder pads may need to be trimmed up to 1 inch to fit. Elbow and back armor should fit correctly without trimming.