We study Borel ideals I on N with the Fréchet property such that its orthogonal I ⊥ is also Borel (where A ∈ I ⊥ iff A ∩ B is finite for all B ∈ I and I is Fréchet if I = I ⊥⊥ ). Let B be the smallest collection of ideals on N containing the ideal of finite sets and closed under countable direct sums and orthogonal. All ideals in B are Fréchet, Borel and have Borel orthogonal. We show that B has exactly ℵ 1 non isomorphic members. The family B can be characterized as the collection of all Borel ideals which are isomorphic to an ideal of the form I wf ↾ A, where I wf is the ideal on N <ω generated by the wellfounded trees. Also, we show that A ⊆ Q is scattered iffis the ideal of well founded subsets of Q. We use the ideals in B to construct ℵ 1 pairwise non homeomorphic countable sequential spaces whose topology is analytic.