Precision 2

As 1 is used for strong hands, weaker hands with have to be opened somewhere else. 2 is used for this. The description of the 2 opening bid is:

2: 6+ or 5 + 4/

Responses to 2:
2 Strong relay, asks opener's distribution
2 5+, constructive NF
2 5+, constructive NF
2NT Balanced invite
3 Preemptive
3// GF, 5+card
1