Subcontracting to subcontractors identified in a tender that was accepted by the  Contracting  authority  and resulted in a signed contract, is considered authorised.  Entities on whose capacities the tenderer relies to fulfil the selection criteria  2.4.3 In order to fulfil the selection criteria a tenderer may also rely on the capacities of other  entities, regardless of the legal nature of the links it has with them. It must in that case prove  that it will have at its disposal the resources necessary for the performance of the contract by  producing a commitment letter in the model attached in  Annex 5.2,  signed by the authorised  representative of such an entity, and the supporting evidence that those other entities have the  respective resources.  If the contract is awarded to a tenderer intending to rely on another entity to meet the  minimum levels of economic and financial capacity, the  Contracting authority may require  the entity to sign the contract or, alternatively, to provide a joint and several first-call financial  guarantee for the performance of the contract.  With regard to technical and professional selection criteria, a tenderer may only rely on the  capacities of other entities where the latter will perform the works or services for which these  capacities are required (i.e. the latter will assume the role of subcontractors).  21  the tenderer still fulfils the selection criteria and the new subcontractor fulfils the  selection criteria applicable to it individually, if any;   the terms of the originally submitted tender are not altered substantially, i.e. all the  tasks assigned to the former subcontractor are taken over by another involved entity,  the change does not make the tender non-compliant with the Tender specifications,  and the evaluation of award criteria of the originally submitted tender is not modified.   Relying on the capacities of other entities is only necessary when the capacity of the  tenderer is not sufficient to fulfil the required minimum levels of capacity. Abstract  commitments that other entities will put resources at the disposal of the tenderer will be  disregarded. 