Build quality of the Canon EF 300mm f/2.8L IS II USM is everything you'd expect at the price, befitting a professional super-telephoto lens designed for the rugged outdoors.
Environmental seals guard against the ingress of dust and moisture, complete with a rubber O-ring in the mounting plate where the lens fixes to the camera.
The use of expensive fluorite lens elements aims to maximise image quality, while the front and rear elements have fluorine coatings on their outer surfaces to enable easier cleaning.
Canon's SWC (SubWavelength Coating) is also used to reduce ghosting and flare.
Not-so-little extras include a whopping lens hood, a soft fabric wraparound lens cap and a custom-made 300B hard case, which is similarly well made and nicely padded.
Switches and control rings all have a high-precision feel to them and handling is excellent, despite the size and weight of the lens.