"This stock does NOT fit the 4200 Mah 9.6 Tenergy battery. Instead of mailing it back, I used a 7/8 in. forstner bit in a drill to enlarge the plastic tubes. The batt's plug was in the wrong place! 4 solders later, I got that monster in there. 5 hours shot. Do yourslf a favor, don't get this for a 4200. Get two 1600's or 2000's and live happily ever after"