Laser diffraction (LD) analysis (MasterSizer-2000, Panalytical) was employed to obtain quantitative size distributions of the MPs. This technique offers high-throughput capabilities, enabling rapid size distribution measurements of large sample volumes with minimal sample preparation beyond dispersion. However, limitations arise when analyzing polydisperse and amorphous MP samples. In polydisperse samples, the overlapping diffraction patterns can lead to an underestimation of smaller particles due to their weaker scattering signals. While sample fractionation could improve resolution, it introduces additional steps and equipment requirements. Moreover, the assumption of sphericity, inherent in LD analysis, neglects particle shape factors, which can introduce inaccuracies in size distribution measurements of amorphous MPs. Finally, the measurement provided by LD analysis is inherently volumeweighted, being a measure of volume fraction. Thus, the lower volume MP measurements carry significant errors and can be 'drowned-out' by the larger volume ones. It is valid to use volume fraction for the size distributions, however, considering that the most significant problem regarding microplastics is that they are highly diffusive, a more suitable statistic is their number fraction distribution, which emphasizes the smallest, most diffuse particle (all size distributions shown in this work are presented as number fractions). All of these factors contribute to a significant mismatch between the size distributions measured with The analytical results for four MP samples which represent some of the most commonly detected MP types, are included in the main manuscript for a deeper discussion: a polyolefin, LDPE; a polyaromatic, PET; a polyamide, Nylon 6; and an elastomer, Silicone. Further examples are given in the SI and only some of the key similarities and differences are referred to in the text. Polyolefins (HDPE, LDPE and PP) represent the most commonly produced plastics worldwide by a considerable margin, with 37.5 % of European plastic production being these 3 species. 44 LDPE alone accounts for 14% of the total European production -being used primarily for the manufacture of single-use plastic bags, food packaging and bottlesand is a significant contributor to MP pollution. Polyethylene Terephthalate (PET) is another of the most widely produced plastics, being used predominantly in the manufacturing of polyester textiles, as well as single-use drinks bottles. As a significant contributor to MP pollution, many studies are focused on the health and environmental impacts of PET MPs as well as strategies to remove, recycle or degrade them. The polyamides Nylon 6 and Nylon 6/6 are widely used for their excellent mechanical strength, being used as fishing lines, packaging, and clothing. As such, they are a commonly found MP in marine environments. Elastomeric materials, such as silicone and rubbers, are not strictly plastics as their constituent polymers are covalently cross-linked. Nonetheless, micro-and nanoscopic elastomers are routinely described as MPs and NPs owing to their similarity in number and effect on an environment. As a representative of the elastomeric materials we selected a silicone elastomer material, obtained by milling a undyed and transparent laboratory bung.