It was during a promotion, which i've seen come up again since I had mine done. $49.99 ea for E2 and SRT mods.
There is an SRT kid on gunbroker now with a starting bid of $80 - I have not yet seen the E2 parts available for separate purchase.
Glock 43 | Glock 26 G4 | Glock 19 G4 BFG | S&W M&P 22 | HK USP 9 | HK USP 45 (Tan) | HK P2000 | HK P30L | HK VP9 | HK 45 C | HK 45 C "Sand" | Walther PPQ 9
Daniel Defense DDM4 V4 | Arsenal SGL 21 | ASA Side-Charger SBR | Savage Mark II FV-SR
Mossberg 590A1 20" SP | Mossberg 500 Cruiser