Fast action bread yeast is a very fine grain of yeast, almost a powder.
It is designed to be mixed straight into dough, right out of the package.
The dough will need only one kneading and one rising.
It is sold in 7 g sachets, made by manufacturers such as Hovis, McDougalls, Harvest Gold, etc. There are also supermarket brands, some of which may be made by the brand name people for them.
It has been available in the UK since at least autumn 2003.
For bread recipes using up to 5 cups (1 1/2 pounds / 750 g) of flour, use 1 sachet.
For bread recipes using up to 10 cups of flour (3 pounds / 1.5 kg) of flour, use 2 sachets.
7 g package = 1 1/2 teaspoons
17 g sachet is equivalent to 1/2 oz (15 g) of fresh yeast