The adjustable stems are not something I would use long term for off-road riding. For riding around the neighborhood, they're fine, but for hitting jumps (even small ones) they're an accident waiting to happen.
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"Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming, "WOW, What a Ride!" - unknown
"Your Bike Sucks" - Sky Yaeger