I needed the head lock down screws for an old carbon tripod I had stashed in a storage room, the tripod not being Manfrotto. I took a chance and hoped these screws would fit, and they do! Exactly what I needed. I think the head lock down screw size is not standardized, as there are also some M5 size screws, but I knew they would be too small. These Manfrotto screws, however, will likely fit most tripods. I really wish such screws would be provided with any head purchased. Shipping from Pictureline was fast, a good company from which to purchase.