[helene_t]

In Wei precision, the 1♣ opening includes 16-21 balanced hands. The 1♦ response shows 0-7.

1♣-(1X)-pass-(pass)
1NT
and
1♣-(pass)-1♦-(1X)
1NT
both show 19-21 since with 16-18 opener can pass.

What about
1♣-(1X)-dbl-(1Y)
1NT?

The double is negative, i.e. either a standard t/o or a somewhat nebolous semipositive (with a semipositive you can also have a penalty pass and in my partnership we play semipositive jump-shifts here so there is some negative inference).

[jtfanclub]

I do not play 1♣-(1X)-pass-(pass)-1NT as 19-21. The two possible hands partner can have are....

1. GF vs. a 16 count, hoping that I'll reopen with an X (which he'll convert), or
2. Insufficient to get to game across a 21 count.

So there's not much of a reason for me to make my bid based on hcp.

1NT shows a hand that believes it can make 1NT across a 2 hcp hand, and has sufficient points in their suit that it cannot believe partner was making a penalty pass. I most likely am not even truly balanced- I would rebid 1NT after a 1♠ overcall with this hand: AJTx Ax x AKxxxx. Most truly balanced hands double, regardless of strength.

I suppose, in theory, there is a hand that would pass that auction, but I have yet to have it. In effect, this auction is forcing. I don't think I'm handling this differently than C.C. Wei would.

1♣-(1X)-dbl-(1Y)-1NT?

That to me shows the 19-21. Pass shows the balanced 16-18, as partner will get another bite at the apple.

[whereagles]

Why would you want to pass 1x out with a bal 16-18? Pard isn't always going to bid with 3-4 hcp and you might have a partscore still.

On pass out seat, 1NT should be 16-21. It is only in the direct seat that it should show extras, because then, if you pass, pard, who still has a bid, will infer you have the bal 16-18.

[awm]

This depends a bit on your style after overcalls too. If partner would bid on absolutely any hand of 5 or more points unless hoping to penalize, it's not unreasonable to pass the board out when opener has a minimum 16 since you're not that likely to make 1NT and you could easily go down a lot if partner has nothing. In this case I wouldn't go so far as to play 1NT rebid as "19-21" but something like 18-bad 21 seems fairly reasonable (passing with 16-17).

On the other hand, I frequently play that double of 1X is "takeout" and partner would normally pass with less than GF values and the wrong shape for a double. So a fair number of balanced 5-7 point hands also pass, in which case it becomes more reasonable to bid 1NT with 16 in balancing seat.