Part of the reason Titleist moved the hybrids to a 16 release was that they are most commonly matched to an iron fitting as 3/4/5 iron replacements. Your choice will be to check your 4I and your next fairway distances, and then get fit to fill your distance gap. If you hit a 3W/15 well, likely you will prefer a 19 or the 19 set to 20 to fill that gap. I had a similar issue with the 23/25 816s but elected to go with the 25 and kept a 915 21.

I replaced my 4 iron with the 816 H2 23, what a difference. I tend to exaggerate fades with long irons, but the hybrid helped play a nice draw on the green about 200 out. Great stick to have in the bag.

I have the 716 AP2 irons and chose the 816 H2 23 to take the place of my 4 iron, very happy with it great for 200 to 210 yards. I have it set at neutral 23 degrees.

Basically your looking to fill the distance gaps between your 4 iron and fairway wood. I carry a 3 iron around 210 & 3 wood around 240, these are carry distances from the turf. This leaves me a 30 yard gap that needs to be filled with a 225 carry distance. I chose a 2 hybrid over the 5 wood to fill this gap. You need to get on a monitor and check your carry numbers and pick the set-up that splits the difference. To make it more confusing, you may consider to pull the 4 iron out for a 19* & 23* hybrid combo option if you need to add a wedge???

I have an H2 19* turned to 18* and love it. it fits my ball flight for that club really well and lands SOFT too. Yesterday was 219 out into a par 5 and hit center of green with about a 10yd roll out. Great club that I have total confidence in. Now the gap between my H2 and my 4 iron if more substantial, but my tee length rarely puts me in the range of a three iron anyway so it works out very well.

Evening all
I currently play a 18° 5 wood and love it, has really helped my game, I want to add to it with a 818 h1 hybrid but not sure 21° or 23° I know I can alter the loft slightly but I'm not sure what's best, my 5 iron is set at 24°, any help or recommendation would be appreciated.
Many thanks

For me it is the 21 degree. I used it a lot more than the 18 degrees. Also, the 21 degrees is easier to hit. It is a very versatile club.

I also have the AP2 716 irons and had a similar issue. I have the 915 hybrids and I've found that with my 5 iron being 27° the 24°,21°& the 18° hybrids fit in well with my 15° 3 wood. On some courses I can take the 3 wood and put in the 18°.
Don't forget the hybrids can be adjusted to suite.

I have pretty much the same setup as the OP, and the 21* makes sense for a number of reasons. First off it blends with the 4 iron, to match the loft of a 3 iron it is replacing. Secondly, the 19* is surprisingly harder to elevate for me, and the 21* is just easier if that makes sense. I can do alot with my 816 H1, so much so I would say its my favorite club. I play my irons +1/2" so I matched the 21* to that, and that means I can really squeeze a couple yard out of when I grip at the end. If I need more finesse I choke it down, and it plays more standard. It may not make that much difference for some, but 19* just seemed to work best off a tee or as a lay up, not as much confidence for going at greens and holding them.