Not sure what is best, just know that I go smaller than a regular 4b. Its default from my coach. I know there is solid reasoning behind it, but can't remember at the moment what that is, but he is good so I trust him. LOL

I guess one thing could be is that a cold 4b already looks super strong and people are tend to fold more to them. So if you have a value hand you want action. If you look at bluffs, then going smaller gets you a cheaper bluff, seeing as people tend to fold more.

My default size in this spot would be like 17bb or 18bb. Going to 20bb+ can't be bad either. It is 5nl so maybe going bigger for value is better and makes SPR smaller on the flop and makes playing post flop easier.

Is that in any 4bet position or just in examples like this one?

I think around 20bb is fine. If they just CC then were going to have to play oop and it could get tricky if we don't improve, so we don't want to inflate the pot too much. But at the same time it gives us enough protection to get some smaller pairs to fold, that would fold post-flop when we connect anyway.

In terms of the opening posters "if we 4bet" question, I think we should almost always 4bet here. Without 4betting we don't really have an idea of where we are post flop against a 3bet from the button. After a open from the CO, a button 3bet is fairly standard and could rep a wide range of hands so their response to a 4bet would tell us where we stand.

Hard for me to say anything different without more info. However, my usual play is to 4bet/call and not mess about 'playing poka' to a minraise and a 3bet, although the 3bet is quite large from an IP opponent; then again I see lots of those as well in my games.

Anyway, it's 4bet to 24bb for me, call it off and go kick the dog (again) if I lose. And if the mrs shouts up to me 'What's wrong now?' try to answer 'nothing love' as calmly as I can.

Easy game.

Without some additional info on the other players in the hand, it's hard to say what would be the optimal 4bet sizing. Fortunately, it doesn't really matter that much, everything between 18-25bb should be perfectly serviceable depending on your overall gameplan. If anything I'd be inclined to go with a slightly higher sizing given the context of NL5 anon game. I can't imagine your bluffing frequency here is terribly high to you might as well emphasize pot management over anything else in this spot.