For the record--the "Beeman" peep sight is indeed made by Williams here in the US. They actually make several models with the same longitudinal-bar-type adjustable mount, that are suitable for airguns.
Their "FP" series are compact sights with clicking elevation and windage adjustments. The model FP-AG is the basic model with screw adjusters, and suitable for a comparatively high sight line seen on most airguns. The FP-AG TK is the same sight with target knobs (and is the variant typically seen in "Beeman" garb).
The FP-GR series has a longer mounting base and lower sight line. These are more intended for rimfire firearms with grooved receivers, though some airguns such as the classic Diana model 50 favor it as well. Again available with screw (FP-GR) or target knob adjusters (FP-GR TK).
Williams has recently introduced a version of their simpler (and much less expensive) "5D" series, with simple screw-slider elevation and windage adjustments, having the versatile bar mount. The 5D-AG is the higher-sight-line version, and 5D-GR the lower one. The 5D series is best known to US airgunners through the 5D-SH which has been a popular upgrade for Benjamin and Sheridan pneumatic rifles for many years.
Their web site very well illustrates all these models.
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