I've had the "m14 medic" brand on a past rifle, fit and worked great. I went the SJ spring guide this time around. I've always been happy with SJ products, and for the same money, it seems to have a much superior coating/finish. I THINK the m14 medic one is just park'd. Again, this is just my opinion, it might not be correct. Both will work great, and side by side I would imagine they would shoot the same.