【Replacement Carbon Core Resin Inner Case for Casio GST-B400 – Middle Shell for G-SHOCK G-STEEL Repair】 – Precision-engineered replacement middle case (中壳/内胶壳) designed for the Casio G-SHOCK GST-B400 series. Compatible with GST-B400, GST-B400-1A, GST-B400BB-1A, GST-B400D, GST-B400AD, and all GST-B400 subseries featuring the 5657 module-. This carbon fiber-reinforced resin inner shell is the critical structural component that houses the ultra-thin 5657 module, maintaining the watch‘s legendary shock resistance while preserving the slimmest profile in the G-STEEL line at just 12.9mm-. The essential replacement part for restoring the structural integrity of your G-STEEL timepiece.
Carbon Core Guard – The Heart of G-STEEL Toughness – The GST-B400 features Casio’s Carbon Core Guard (碳核心防护构造) – a carbon fiber-reinforced resin case that ensures shock resistance while reducing weight-. This inner case is the structural foundation of the watch, absorbing external shocks and protecting the ultra-thin 5657 module-. Without a properly fitted inner case, the watch’s shock resistance and water resistance are compromised. The design is built around a double-layer bezel construction of stainless steel and resin, delivering the hard, sleek beauty of metal while retaining the impact absorption of resin-.
Precision Fit for GST-B400 Series – Specifically engineered for the GST-B400 platform. Compatible with all subseries including GST-B400-1A, GST-B400BB-1A, GST-B400D-1A, GST-B400AD-1A4, GST-B400CX, and GST-B400X models-. The precision-molded design matches the 46.6 × 49.6 × 12.9 mm case dimensions-. Please confirm your watch model – different G-SHOCK series use different inner case specifications.
Premium Carbon Fiber-Reinforced Resin – Lightweight & Durable – Crafted from carbon fiber-reinforced resin – the same material used in the original GST-B400 construction-. Key advantages:
Ultra-lightweight – contributes to the GST-B400’s 80g total weight-
Impact-resistant – absorbs shocks to protect the module
Thin yet strong – enables the 12.9mm slimmest G-STEEL profile-
Maintains 200m water resistance – when properly installed with配套防水圈-
Essential for Watch Restoration & Module Transfer – The inner case is the critical structural component that must be replaced if cracked, warped, or damaged. Perfect for:
Replacing a cracked or damaged inner case – restore structural integrity
Completing full case restorations – the essential foundation for any GST-B400 rebuild
Module transfer projects – move your 5657 module to a fresh inner case-
Restoring water resistance – a damaged inner case compromises the 200m seal-
Professional Installation Required – Replacing the inner case requires full watch disassembly – removing the bezel, extracting the 5657 module, and reassembling with precision-. The GST-B400’s ultra-thin 12.9mm construction- means internal tolerances are extremely tight. Professional installation is strongly recommended. Installation requires proper sealing to maintain 200m water resistance-. This is an aftermarket replacement part, not a genuine Casio® part. However, it is precision-engineered to match the original specifications used in Casio GST-B400 watches.
