http://www.keystonecountrystore.com/Blackpowder/RMC/RMC_V-Peep_Sight_TC_Models_with_5_x_16_Octagon/Page_1/BLK3057607.html
Some times a picture helps try this site.
There is also another option, In states where I can not use a scope so my poor old eyes can focus I put a Ghost peep in back and a shielded home made front ring peep in front this lets me focus on the target and avoid the problems my tri focals cause. Lee