It's likely to be a mixture of about 65% sodium percarbonate and 35% sodium carbonate... (you might find that buying pure Sodium Percarbonate is actually cheaper)
As @Brianbrewed says, do make sure it's not the fragranced stuff.
Just be aware that:
it efervesces quite vigorously (producing oxygen) so do NOT seal up the vessel your cleaning or it might burst
it's more effective if used hot
the solution needs to be used within 1h, after which it breaks down into pretty neutral byproducts
I'd recommend soaking for a max of 30min and then rinsing off, because if you soak for too long then you can get a cloudy deposit that's annoying to remove
I don't personally find it necessary to use gloves with sodium percarbonate (YMMV)
It's likely to be a mixture of about 65% sodium percarbonate and 35% sodium carbonate... (you might find that buying pure Sodium Percarbonate is actually cheaper)
If anyone can find pure Sodium Percarbonate that's as cheap as the 2kg tub of Astonish Oxy Active then I would be very interested as I've never been able to find anything that comes even close.