Overview & Obtaining
Dusters are currently one of two available hot-weather garments available in the game - the other being the cowboy hat. As parkas are necessary to survive in very cold biomes; Dusters are necessary to survive in very hot biomes (e.g. Arid Shrubland, Tropical Rainforest, Desert etc.), and recommended for temperate biomes (i.e. Temperate Forest), as both are suspect to heat waves and the former can handily reach around - or even exceed 60 degrees Celsius at the peak of summer. Dusters can be purchased from traders, crafted, or stripped from Outlanders and Pirates.
As a complicated garment, dusters which requires complex clothing to be researched and can only be made at a hand-tailoring bench or an electric tailoring bench. A duster requires 80 of any textile, and 367 seconds of work (22,000 ticks) to be created, assuming baseline global work speed and no enhancements or hindrances to consciousness, sight, or manipulation.
Conclusion and Comparison
Dusters are overall superior to jackets in the respect that dusters have the same base cold insulation, but covers more body parts (torso, shoulders, arms and legs), and also offers blunt protection - at the slight cost of sharp protection (7% vs 8%). A duster made out of any wool provides cold insulation on par with that of a standard parka, along with heat insulation, less movement penalty, and no penalty to overall global work speed.
The following table(s) will display how good a normal quality duster is at insulating when made from various materials...