Product Description: Block size is 2.2 x 2.2 x 0.5 cm (expected to yield ~40-50 sections of ~4-5 μm thickness), but can vary slightly. Cell pellet consists of 293T cells overexpressing SARS-CoV-2 (COVID-19) Spike (Omicron / BA.4 / BA.5) fixed with 4% PFA (15 min, room temp) 48 hrs post-transfection, and then embedded in paraffin.