(23)In some Member States, there are certain legacy payment services which are credit transfers or direct debits but which have very specific functionalities, often due to historical or legal reasons. The transaction volume of such services is usually marginal. Such services could therefore be classified as niche products. A transitional period for such niche products, sufficiently long to minimise the impact of migration on PSUs, should help both sides of the market to focus first on the migration of the bulk of credit transfers and direct debits, thereby allowing the majority of the potential benefits of an integrated payments market in the Union to be reaped earlier. In some Member States, specific direct debit instruments exist which seem very similar to payment card transactions in that the payer uses a card at the point of sale to initiate the payment transaction but the underlying payment transaction is a direct debit. In such payment transactions the card is used only for a read-out in order to facilitate the electronic generation of the mandate, which has to be signed by the payer at the point of sale. Although such payment services cannot be classified as a niche product, there is a need for a transitional period in relation to such payment services because of the substantial transaction volume involved. In order to enable the stakeholders to implement an adequate SEPA substitute, that transitional period should be of sufficient length.