, purest high quality oil with guaranteed gla level fantastic value for pharma grade oil, also contains vitamin e for added freshness smaller pot sizes freshness guaranteed, to pharmaceutical standardsevening primrose oil is a still one of our most popular products & this 1000mg version offers excellent value for money. we use only the purest oil in our capsules with a guaranteed level of 9% gla. this omega 6 fatty acid is the active ingredient in evening primrose oil & the amount present determines the quality & price of the oil. there is a big variation between oils & ours is carefully selected & then tested to ensure it contains at least 9% gla. our tests indicate that not all the products available meet the level of gla declared on the label.the oil from borage seeds generally called starflower oil is also a rich source of gla & in our range we offer a pure starflower oil with 22% gla & a 12% gla evening primrose oil which is fortified with starflower oil.