FOC=Forward only conversion. The Revo has a reverse gear set stock, the FOC just eliminates the reverse parts (and removes a fair bit of weight too). The FOC kit comes with two of those pins, which are black. The stock pins are chrome and seem to not be quite as strong, but that is pure speculation.
now i feel like a idiot FOC couldnt figure out Conversion lol yea i think i will be back in mine to put better pins is going to be easy now that i looked at it will be locking it in 2nd also