BIRCH core muaj nuj nqi mechanism txais German imported BOCK hlau tswj chassis, nruab nrog high-kev ua tau zoo configuration, tag nrho-round kom tau raws li cov neeg siv cov kev xav tau: lub rooj lifting muaj nuj nqi, cushion zawv zawg muaj nuj nqi, lub rooj zaum rov qab peb-theem tilting locking muaj nuj nqi, tilting lub zog ceev hloov muaj nuj nqi.