the category C2V, of topological vector locally convex Hausdorff spaces in the class of c-reflective subcategories Rc, a binary operation is introduced so that Rc becomes a groupoid (commutative, with neutral element, any element is its symmetric). Rc is the class of reflective subcategories L that contain the subcategory of spaces with weak topology S and the reflective functor l : C2V −→ L is exactly on the left. Such subcategories are S, the subcategory of ultranuclear spaces, Schwartz spaces, etc. (see [2]). Let L, R ∈ R be and ρ(L,R) the full subcategory of the category C2V, of those objects A, for which the L-replica and R-replica are isomorphic: lX = rX. For L ∈ R let εL = {e ∈ Epi|l(e) ∈ Iso}. Theorem Let L, R ∈ Rc and B = (εL) ∩ (εR) be. Then: 1. ρ(L,R) is a reflective subcategory and S ⊂ ρ(L,R). 2. ρ(L,R) is closed in relation to B-subobjects and B-factorobjects: ρ(L,R) is a B-semireflexive subcategory [1]. Any reflective subcategory that contains subcategory S also contains the largest c-reflective subcategory. For ρ(L,R) we note it ρ(L,R). The binary operation L⊕R = ρ(L,R) in the class Rc possesses the following properties: 1. It is a commutative operation: L⊕R = R⊕L. 2. The element C2V ∈ Rc is a neutral element: L ⊕ C2V = L.3. Any element L ∈ Rc is also its symmetrical: L⊕L = C2V.