For all the people that can't understand why Glock made this........ Here is why, there is a market and other manufacturers are making money extending the grip while only adding 2 rounds from Strike Industries, True Precision and Shield Arms to name a few.
Companies milling RMR cuts = Glock Factory RMR cuts
Companies making forward serrations = Glock factory forward serrations
Companies making Plus 2 grip extensions for G43 = G43X
That doesn't explain what Glock did.
People don't always trust aftermarket mag extentions over a true purpose-built product.
If Glock wanted to, they could easily make and sell their own extended mag, and have it be a pure Glock company product.
They're selling this because they know they can milk the market, then sell a thinner one later. Why sell people one perfect pistol, when they can get people to buy 1 or 2 others along the way?