O.S. stands for Overpriced S--t. Look at the TSI .40 At www.kangkeusa.com. I have two and they are super. Also check out the MECOA .40 at www.mecoa.com. Both are BB ABC engines and cost about $60.00. Irvines are nice (I have three, a .40, a.40 diesel and a.21) but they are simply underpowered compared to most. The best for the money, in my opinion, is the Enya. They are bulletproof and I have a few that are twenty years old and are still strong.

Good Luck,
Max