These small reflex sights from Docter, well, replicas of these, are popular amongst airsoft players as they are useful backups for their scopes and magnified sights. Alexander of the Red Army Airsoft Club reviews a replica of the Docter Sigh II Plus which he finds has good build quality and it's small size and reliable abjustment makes it useful when installed on blowback pistols. He just finds it that it's totally useless in dark conditions.