Why does the size of smokeless coal matter?
Larger sized briquettes like Homefire and Ecoal50 give a more authentic looking fire, as they look like lumps of coal and more importantly there are large gaps between the briquettes for better air flow leading to bigger and better flames. Larger sized briquettes are recommended for open fires and glass fronted stoves.
Small size briquettes like Phurnacite or Stoveheat sacrifice visual appeal for increased heat output and longer firelife. Their small size means they pack together into a tight firebed, which restricts air flow so that they burn with a super intense glow, radiating heat for up to 18 hours (Phurnacite under ideal conditions). Small sized briquettes are recommended for closed appliances such as cookers, boilers and roomheaters.
Mid-size briquettes such as Taybrite are a compromise between visual appeal and firelife and are consequently recommended for use on all appliance types and open fires.
Ultimately all our fuels work on all types of open fires and appliances (with the exception of gravity fed boilers), so the choice of which fuel is best for you, comes down to what properties of the fire you value most.