Rear sight fits nominal 3/8" dovetail. Uses same blade as the Williams WGOS rear sight. This sight does not come with a blade. It must be purchased separately.Notes:If WDOS is used with 3/16" blade, height is adjustable from .281 to .345If WDOS is used with 1/4" blade, height is adjustable from .345 to .406If WDOS is used with 5/16" blade, height is adjustable from .406 to .468If WDOS is used with 3/8" blade, height is adjustable from .468 to .531