These are you basic upgrade die cast M4 hopup unit. These offer superior rigidity and support than plastic models.and smooth feeding. The adjustments on these have good holding force so they won't move from vibration or BB pressure. To gain maximum performance out of these (or any hopup unit) I would recommend shimming the hopup arm to totally reduce any play.
This product was added to our catalog on Thursday 24 April, 2014.
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