Understanding the translocation of soft, conformable single-chain polymer nanoparticles (SCNPs) with intricate topology through nanopores and nanoslits is of great interest for several potential applications, including modern single-molecule analytical characterization methods. This work focus on the ultrafiltration of an elastic SCNP of size R through a cylindrical pore of diameter D <<R or a rectangular slit of width H <<R under an elongational flow field. Concerning SCNP ultrafiltration through nanopores of different diameter, we find a scaling law in qualitative agreement with recent results concerning the ability of soft conformable nanoparticles to translocate through pores at least tenfold smaller in size. Moreover, SCNP ultrafiltration through rectangular nanoslits provides a simple way to determine the elasticity parameter of a real SCNP based on its experimentally determined minimum slit width for effective ultrafiltration. (C) 2018 Elsevier Ltd. All rights reserved.