I started to use the Muzzy MX-4's after wanting to get away from Thunderheads as well. It wasnt so much the O-ring issue with me as much as a consistancy and lack of penetration issue. Ever since I switched to the Muzzy MX-4's my arrow placement is more consistant and every deer I have shot with them have been complete pass throughs. I never had one pass through with the thunderheads.