ARMS SIR rail question

[cgseanp1]

[ar15barrels]

Recently purchased an upper with ARMS SIR rail.. the rail feels like plastic.. not super cheap feeling, but still it’s like a polymer or plastic. What material were the ARMS rails made of?

I have a 50SM and 58SM, both seem to be same material.

Thanks

The upper rail that clamps on the reciever is aluminum.
The lower section that you grip with your hands is plastic.
This keeps it from getting hot like an all metal rail does.

[cgseanp1]

The upper rail that clamps on the reciever is aluminum.
The lower section that you grip with your hands is plastic.
This keeps it from getting hot like an all metal rail does.

Thanks for info.