The 4100 half-zip turtleneck sweater lists M through 2XL in Gray and Black. Its model note describes L as fitted and XL as loose for one person. That sounds like a large change, yet the chest column moves only 2 cm between those sizes. Use the note as a prompt to check the numbers, not as a rule based on height or weight.

Read all four columns at the same step

The source chart labels chest “CIR” and lists M/L/XL/2XL at 118/120/122/124 cm. Over the same sizes, length is 72/73/74/75 cm, shoulder is 75/77/79/81 cm and sleeve is 49/51/53/55 cm. Moving from L to XL therefore adds 2 cm to listed chest, 2 cm to shoulder and sleeve, but 1 cm to body length. The chart does not define its measurement points or say explicitly whether “chest CIR” is a finished sweater circumference or a body recommendation. Ask for that convention before using the figures to calculate ease.

Use the model note for a question, not a formula

The listing includes heights, weights and worn sizes for several models; one note calls L fitted and XL loose. It does not provide each model’s chest measurement, preferred layer or how those words were judged. A different wearer may feel a different change between a 120 cm and a 122 cm chart value. If the fit of a sweater you own is right, record its chest, shoulder, sleeve and length at matching points and compare all four with the listed rows. If your reference falls close to a boundary, ask the seller how these measurements were taken and what tolerance applies. Neither the model’s weight nor a letter size resolves that uncertainty.

Make the half-zip a separate check

The source identifies a 100% cotton long-sleeve turtleneck with a half zip. It gives no neck-opening size or zip depth. If you intend to wear the collar closed under a coat or open above a shirt, compare those positions with a half-zip you own and request the missing collar dimensions if they affect your choice. The chart can help compare body dimensions; it cannot prove that a particular collar or layer combination will feel right.

Choose a provisional size from the four measurements you can compare, then resolve the missing convention where a 2 cm chest step would change your decision. For broader chart-reading advice, see the garment-versus-body measurement guide.