Scorpyon Tec Venom Peep. 

Self-aligning peep that uses a solid tether that is durable and is highly elastic. The peep is Horizon blue which is the same color as the atmosphere in pre-dawn and post-sundown light conditions. The tether is pulled through the peep and then attached to the cable with a clamp which is included in the kit along with the peep and two tethers. It is quiet, durable and performs in cold weather.