To interlock the two Air Circuit breakers ( ACBs ) using the same key, we need to orderfollowing catalogue numbers :-

From Ronis series :-
Adaptor # Part code - 48539 , Qty.- 2 nos need to be ordered
Locking Kit # Part code - 48564, Qty.- 2nos need to be ordered
2 Key Lock with same profile #  Part code -41950, Qty. - 1no need to be ordered