Helix Universal Brake Residual Check Valve. For vehicles with master cylinder mounted below brake calipers, this residual check valve is designed to prevent brake fluid back flow and maintain fluid pressure to the brake calipers. Main application is for under-floorboard mounted master cylinder and its universal design fits many applications. Input thread 3/8-24 with 3/16” thread at output compression fitting. Attractive blue color matches well with braided stainless lines and other Helix accessories. Standard duty 2 lb. Stay ahead of the pack with Helix Suspension.