A watch housing comprising: a main body having a first opening and a band retaining feature comprising a channel configured to receive an attachment unit of a watchband to be removably coupled to the main body; a rear cover having a second opening, wherein the first opening and the second opening are connected to form a continuous space within the watch housing; a button comprising a flange and extending at least partially through the first opening and second opening, wherein: the flange is between a rear portion of the button and a channel portion of the button and the button is moveable between a first position with the channel portion entirely within the first opening and a second position with the rear portion entirely within the second opening, the button is: accessible by a user through the second opening, at least partially between the main body and the rear cover, biased toward the rear cover, wherein when the button is depressed it is configured to release the attachment unit from the band retaining feature, and wherein movement of the button with respect to the band retaining feature is limited by the main body, biased to a rest position in which the button rests against the rear cover, moveable toward the channel until a surface of the button is flush and continuous with a surface of the channel; and a spring element between the flange and the main body characterised in that the first opening is configured to removably receive a lug of the attachment unit when the lug is aligned with the first opening and the button is configured to expel the lug from the first opening when the button is actuated. a main body having a first opening and a band retaining feature comprising a channel configured to receive an attachment unit of a watchband to be removably coupled to the main body; a rear cover having a second opening, wherein the first opening and the second opening are connected to form a continuous space within the watch housing; a button comprising a flange and extending at least partially through the first opening and second opening, wherein: the flange is between a rear portion of the button and a channel portion of the button and the button is moveable between a first position with the channel portion entirely within the first opening and a second position with the rear portion entirely within the second opening, the button is: accessible by a user through the second opening, at least partially between the main body and the rear cover, biased toward the rear cover, wherein when the button is depressed it is configured to release the attachment unit from the band retaining feature, and wherein movement of the button with respect to the band retaining feature is limited by the main body, biased to a rest position in which the button rests against the rear cover, moveable toward the channel until a surface of the button is flush and continuous with a surface of the channel; and the flange is between a rear portion of the button and a channel portion of the button and the button is moveable between a first position with the channel portion entirely within the first opening and a second position with the rear portion entirely within the second opening, the button is: accessible by a user through the second opening, at least partially between the main body and the rear cover, biased toward the rear cover, wherein when the button is depressed it is configured to release the attachment unit from the band retaining feature, and wherein movement of the button with respect to the band retaining feature is limited by the main body, biased to a rest position in which the button rests against the rear cover, moveable toward the channel until a surface of the button is flush and continuous with a surface of the channel; and accessible by a user through the second opening, at least partially between the main body and the rear cover, biased toward the rear cover, wherein when the button is depressed it is configured to release the attachment unit from the band retaining feature, and wherein movement of the button with respect to the band retaining feature is limited by the main body, biased to a rest position in which the button rests against the rear cover, moveable toward the channel until a surface of the button is flush and continuous with a surface of the channel; and a spring element between the flange and the main body characterised in that the first opening is configured to removably receive a lug of the attachment unit when the lug is aligned with the first opening and the button is configured to expel the lug from the first opening when the button is actuated.