Needless to say this represents a significant upgrade to Iran’s air defense capabilities:

One of the world’s most advanced air defense missiles, the S-300PMU1 Favorit (SA-20 Gargoyle), is designed to protect fixed sites against missile and air attacks. The system uses wheeled transporters for mobility. The Favorit system fires the 48H6E2 interceptor missile, updated with improved guidance algorithms, an improved warhead and enhanced ECCM capabilities. The system detects targets at ranges of up to 300 km and can handle up to 100 simultaneous tracks. Up to 36 interceptor missiles can engage targets simultaneously. Aircraft targets can be engaged between 3 and 200 km, and missiles can be intercepted at ranges of 5 – 40 km, and from 30 to 90,000 feet in altitude.

Against a stealthy target you could figure an engagement range in the 15 km range, based on the engagement distance being proportional to the 4th route of RCS, which means that they are not particularly effective for area defense, but for point defense of a specific target (nuclear facility) it could complicate the attack.

First a report of sale, now a report of delivery, in the space of a week and it looks like some are going to the Syrians too, though it appears to be a fixed installation geared toward protecting a Russian naval base at Tartous, and it is unclear as to whether the operators would be Russian or Syrian.