Petzl E44850 Lens Filter Kit for Tikkina, Tikka, Zipka, Tikka Plus, Zipka Plus, Red, Green, Transparent

As the other review mentions, the "red" filter really isn't. It's closer to orange & didn't seem to do much at all for night vision. The filters are not very easy to swap out but are easy to lose.

If you're looking for that capability & happened to purchase a Petzl headlamp w/o the flip-down or permanent REAL red filter, I guess this is an acceptable cheap substitute. A better option is to return your other headlamp & buy the other model, which is available on here. It costs about the same as purchasing another model plus these filters.
Petzl Tactikka Plus 4-LED Headlamp, Black #E49P

Princeton Tec also makes good headlamps (incl waterproof models) but there aren't many listed on here & I don't know if they offer red-light filters.

First, a small disclaimer; I'm not an outdoors type person. I have a headlamp purely for fun.

I bought this with the savings on the headlamp. The lens filters are constructed with the same high quality standards as all Petzl products.

However, the red filter is a very mild red. To me, it almost looks more like a darker orange than a full red. In fact, when the headlamp is on, it casts an orange light with the middle of the beam (almost) a pink (from the mixing of the bluish light from the headlamp and the filter). I'm guessing Petzl used a lighter red to keep the brightness of the headlamp up, but I would have much preferred to have less light and a darker red.

I didn't spend as much time with the green filter, but I will note that it has a slight teal tint to it.

As far as the purpose of having a red filter to help preserve your night-vision, I can't say that I noticed any benefit to installing the red (or the green) filter.