Interlocking snap-together tubing that can hold its position reasonably well. I'm using it for re-positionable GoPro mounts.
It is compatible with commercial interlocking tube of similar diameter. In all honesty, it is not as air-tight as the real thing and doesn't have quite the holding power but for fairly simple tasks it works just fine. As I'm printing with a standard FDM printer it can be difficult to snap and adjust initially but as some of the layers wear down it loosens up.
I've printed a thousand of these however I'm still tweaking it every now and then.
Print the standard interlocking tube upside-down (small hole on the bed) as the pressed layers can make it harder to snap. The GoPro mount should be printed with supports.
I prefer PETG for these as it has more give before breaking.