The difference is the sequence contact.
QR/P1-PCA2B-221
: Sequence contact
QR/P1-PC2B-221(12)
: Not sequence contact
Applicator is the same. Applicator part number is AP105-QR/P1-2B-2.
QR/P1-PCA2B-221 is sequence contact that contacts with the other connector first at mating,
when QR/P1-PCA2B-221 and QR/P1-PC2B-221(12) are used together.
Both contacts can be used for QR/P1-xxPC-C(50).
Note: "xx" stands for number of pin.
Example: QR/P1-16PC-C(50).