www.rmcsports.com check out theirv-peep sight that they invented for bad eyes etc. i got one and like it and i hunt with it for deer. top of peep is cut -out.it has no insert.it is real thin,about 1/8 inch thick on rear sight. i like the green insert for front sight,they come with red one.you can buy spare inserts for front . i did because you never know when one may break. i hated the original sights and i tried the fiber rear ones and they were blurry on my eyes. the owner of RMC invented this.it is working fine for me. this sight has made it fun to shoot and hunt. type in search at site, V-PEEP. my model was ML-230-3 for .50 caltc hawkins.