The Red Mason Bee (Osmia bicornis) is about the same body size as the European Honeybee (Apis mellifera).
Females are larger than males.
Males have gray-white hairs on their faces while females have black facial hair.
In addition, males have long antenna while females have short antenna.
These bees are not aggressive.
The photos show a male; the bee on the last photo is much more black than the ones on the other photos.
Landgoed Oostbroek, De Bilt, The Netherlands, 11 April 2019