What is the "best" or most reliable +2 mag extensions for the 9mm Shield. Taking the 7 round mag to 9 or the 8 rounder to 10.

Magguts looks to be pretty good, but that's just from a few reviews I've seen.

Magguts here, couple thousand rounds with no issues.

I prefer the Strike Industries +2 extension on the 7 round magazine. They are about half the price of many others two. For Strike M&P Magazine SHIELD +2-Round EMP Industries 9mm/40 S&W Plus Extension | eBay

Here is another one that looks identical but even less expensive. Solid Enhanced Magazine Extension Plate 2 Rounds For 40 S&W M&P-SHIELD 9mm | eBay

I didn't see an added length measurement on that Strike Industries. How much longer would you say it is?

I don't know but have 2 coming from HYVE. They do take about 12 days to ship but that may because there are so many color combinations offered and they need to make them. Anyway, I will report in on reliability.

I would say it is about 3/8" longer than the 8 round magazine, or about the diameter of a bullet. Here is a side by side picture.

Attached Images

8 vs 9 round shield.jpg (37.0 KB, 62 views)

I’ve only tried MagGuts. I have 4 for two different Shields. Excellent through many hundreds of rounds each, a couple thousand total. It’s not just an extension but a very competent spring system also.

Others may be as good. I don’t know. Others are certainly cheaper, but that does not mean better. The actual increased cost of MagGuts amortized over a number of years is insignificant to me.

Another vote for MagGuts. (Gen1 or Gen2)
I've been using them in my Shield 7 & 8 round mags since they were introduced.

I didn't get them strictly for the extra capacity though... I got them to make the 7 round mags easier to fill to capacity and easier to lock into the mag well.

I use the Strike Industry's extensions. They work great.