Maruha BC Damper — Pro Street Coilover · NA/NB Miata 1990–2005
Custom-built by Buddy Club Japan to Maruha's exact engineering specification — not to be confused with BC Racing. The BC Damper is a bespoke, made-to-order suspension system developed in Shizuoka and tuned specifically for the Miata chassis through decades of Maruha circuit testing and street refinement. It features the largest piston diameter available on any Miata coilover on the market.
Technical Specifications (from Maruha Motors Japan):

Damper piston diameter: 46.0mm — largest in the Miata coilover class
15-step damping adjustment via top click shaft
Spring rates: Front 8.0 kg/mm · Rear 6.0 kg/mm (base)
Hard use capability: Front 12.0 kg/mm · Rear 10.0 kg/mm
Extended rear upper mount: 20mm additional stroke — eliminates the bounce common to lowered Miatas
Off-black plated drawn steel wire piston for sustained low friction and anti-abrasion performance
NB-style OEM upper mount — compatible with NA and NB chassis
Full ride height adjustment via bottom bracket — independent of spring preload
Overhaul (O/H) capable — absorber body available as standalone replacement

Fitment: Mazda Miata MX-5 NA (1990–1997) and NB (1998–2005) — all variants.
Made in Japan. Production lead time 2–3 months. Authorized Maruha import by Chikara Motorsports — North America's only official Maruha dealer.