 An SP-class of \(L\)-algebras is a class of \(L\)-algebras that contains a trivial algebra and is closed under isomorphic images, subalgebras, and direct products. Thus quasivarieties and varieties are all SP-classes. The SP-class generated by a class \(\bK\) of \(L\)-algebras is the least class of \(L\)-algebras that includes \(\bK\), the trivial algebras and is closed under subalgebras, direct products and isomorphic images.