The carbide triangle TCGX Turning Inserts are for holders STAC, STEC, STNC, STUC, etc.
The inserts are for cutting aluminum.
The positive-rake feature enables the inserts to have an edge that is less than 90° to sit flat in the insert holder for improved cutting clearance and a better finish than negative-rake ones. The inserts have cutting edges on 1 side.
When a cutting edge becomes dull, you just need to rotate the insert in the holder to use the sharp edge. When you buy the replacement inserts, be noted that the larger nose angles and larger tip radii enable a stronger cutting edge, but they result in increased vibration and a rougher finish.