Black Cube Corner Connector
These are a really compact way to connect two or three lengths of V-Slot extrusion together - perfect for corners!
They're machined from a solid block of aluminium, which means they're very, very strong! They're then anodised black for a nice surface finish, and can bring the understated and professional look to any build.
You'll likely want to pair these connectors with two or three 8mm M5 low profile screws and M5 T-Nuts if you're using them to join lengths of V-Slot.