Bosch, the largest supplier of automotive components to original equipment manufacturers (OEMs), on Tuesday reported 33.5 per cent rise in net profit at Rs 281 crore for the fourth quarter ended December 31 compared to the corresponding quarter previous year. The net sales for the quarter grew 11.4 per cent to Rs 1,918.5 crore compared to the same quarter last year. The rise in profits is mainly attributed to a good growth in the after market sales, improved margins and higher treasury income, which went up by 80 per cent year on year at Rs 100 crore. The operating margins improved from 15.2 per cent in December quarter of 2010 to 15.7 per cent in 2011.