Importers of HS 3903.90 (methyl methacrylate-butadiene-styrene (mbs) copolymers) from Korea, South actually paid 11.58% on the taxed portion of the value in 2026-06 — 11.58% across everything shipped, taxed or not. Measured from official duty receipts, not the rulebook: the statutory MFN base rate on this code is 6.5%. Over the window the rate on the taxed portion moved 6.5% → 11.58%, with the largest single step -6.5pp in 2024-09. Measured from official US duty receipts · as-of 2026-06 · confidence: measured, not modelled. The HTS base rate is 6.5% — importers actually paid 11.58%, so the trade-war overlay added 5.1 pts, measured at the border (not a summed rulebook estimate). Reproduce exactly: tariff_story(hs: "3903.90", origin: "Korea, South") · see it at trimtabist.com/tariffs
HS 3903.90. The schedule base rate is 6.5%; importers from South Korea actually paid 11.58% on the dutiable value in 2026-06 — the trade-war overlay added 5.1 points, measured at the border. Measured, not modelled.
Over the window the collected rate moved 6.5% (2023-07) → 11.58% (2026-06), largest single step -6.5pp in 2024-09.
Korea, South's lower duty (11.58% vs 33.9%) lets it price up to 20% above China at the factory and still match on duty-inclusive customs cost. But on the LATEST measured prices, Korea, South actually lands cheaper — $2.62/kg vs $7.81/kg (duty in, freight out).
All goods from South Korea · the whole tariff ledger · reproduce: tariff_story(hs: "3903.90", origin: "South Korea") via /connect. Not customs or legal advice.