Small form factor pallet assembly, comprising a slotted plate having at opposite ends a mandrel drive assembly and an idler assembly, each with end fittings for engaging the drive and manifold block of a cascade-type scrubber permits scrubbing of SFF substrates by replacement of LFF scrub brushes with the SFF pallet. The SFF pallet slot is oriented below its brush nip so SSF substrates can engage the LFF rotation belt and transport drive. The drive chain is fitted with multi-finger yokes of different sizes so that several sizes of SFF substrates can be scrubbed in the pallet with a single chain. Trolleys for lateral transport of substrates from the input zone to the scrubber lane and from it to the output bay are disclosed. The inventive SFF pallet system meets the changing needs of the hard drive industry, and its retrofit capacity extends the life of already-installed LFF cascade scrubbers.