Best way to achieve the triangle caret indicator

I'm trying to figure out the best way to achieve this little triangle indicator using only CSS, do you guys have any tips?

http://ift.tt/1jgYUNC

Epic visual tool

Epson 5030UB 2D/3D 1080p 3LCD Projector Submitted November 23, 2015 at 10:59PM by flux9 http://ift.tt/1jgYUNE