Invictus Practical 4our sQuare Quad with Tek Loc
The Invictus Practical AARM/S 4our sQuare is a robust four-round shotshell caddy system, equally suited to both the Quad-Load and Load-Two techniques, Comes with a Tek-Lok and attaches via two 18-8 stainless binding posts for the simplest, strongest, lowest-profile solution possible - which will never, ever, rotate. Currently available in 12 ga. only. Price is $44.
Check out this demo video with the similar 2.8 caddy: