Light Grey Single Roll

From the Feather Friendly® website:

"Feather Friendly® window markers are an easy-to-use scientifically proven solution for preventing bird collisions with glass surfaces. Feather Friendly® window markers are highly effective in making the area visible to birds and preventing deadly collisions while remaining unobtrusive to humans."
APPROVED BY:
FLAP Canada, Audubon, American Bird Conservatory

Light Grey markers are recommended for most reflective or mirrored areas. Light grey is much more visible on  glass, and is effective at preventing bird window collisions.