These are seconds stock with small chips that do not affect performance.

Fair-Rite 5943002701 MnZn Ferrite Toroid, 43 material, for EMI suppression between 20 and 250MHz, and wideband transformers up to 50MHz.  ui=800. These are ideal for use as noise or common mode suppressors on cables to reduce interference on the HF bands, or constructing baluns.  These are recommended for use on HDMI cables where the cable connects to the computer video card to suppress noise in the 3 to 20MHz bands.

Size: Diameter 35.35mm, Height 12.7mm Hole Size 23mm, color Grey, Fair-Rite PN# 5943002701

For a 49:1 Transformer, a single core is maybe 80% efficient and will run cool enough up to 30 Watts CW or FT8.  Stack two core for higher efficiency and a higher power rating.

See W1CG Low Power Balun Manual for more information on making a 4:1 Balun.