The lower itself is steel. the plastic portion is more of a shroud. On the 7.62x39 version it can be removed and a normal galil pistol grip can be installed(although you would lack a trigger guard). Somoe people have riveted the original galil mag release and trigger guard on as well. This picture shows the set up well:
Here is a picture of a modified galil ace with a classic galil trigger guard and mag release installed:
On the 7.62NATO variant this plastic shroud retains the magazine and is therefore needed to function.
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