Yeah, I know this is an old post.

The current SD pistol is the compact size. The original Sigma F had the 4.5" barrel. The compact version has the 4" barrel. The F was discontinued after the first generation of the sigma I believe and now the 4" is the standard size. Seems they dropped the C off the model number also. The original "compact" has the 14 round 40 mag and 16 round 9mm mag which they still come with. The F models came with the 15 round 40 and 17 round 9mm mag.

Rosewood