I searched this subject, but didn't find any help.

I just bought a lighting kit, and it came with bunch of Scrims, in different sizes. what are they used for exactely?

Scrims are a bit like neutral density filters. That is, they reduce the amount of light emitted by the lighting instrument.

They are frames with wire meshes that mount to the front of the light. The denser the mesh the greater the light reduction.

A scrim is a piece of wire mesh that when placed over the light face, reduces the light output of the fixture. They come in all flavors. A single reduces light by one half stop (1/4 of the light output) or a double is a full stop (halves the light output).

You can also buy half scrims where half is clear and half is mesh or even graduated scrims.

Look at it as a dimmer.

Edit
Ya snuck up on me Ken. I didn't see your post when i answered.

It may be worth mentioning that for those who wonder "if it's like a dimmer, why not just use a dimmer" is that other than being a simple and low-tech way to reduce the output of the light, scrims will not change the color temperature of the light whereas dimming will (the output will become progressively warmer as the unit is dimmed).

thanx for the reply all.

Would it be possible to place a gel shuch as a Rosco Light Frost in front of the scrim to diffuse the light or is the scrim kinda already doing that. I'm thinking in terms of the fill light which I would like to weaken its light output but also diffues it. Thanks

Scrims do not difuse the light, only cut down the output. Diffusion will by nature also reduce the light transmission while softening the beam. If you intend to diffuse the light, add the frost first and then if you still need to cut down the intensity, you can either double up or use stronger diffusion, if desired, or add a scrim.

The closer the diffusion is to the light, the less effect it will have. Dropping a small square or circle of diffusion into the slot where the scrims go will have less of a softening effect than if you clipped a larger piece to the barn doors, and so on. However, the intensity will not be affected.