SHANGHAI Haixin's foreigners-only B shares marked their debut on the Shanghai stock exchange yesterday with a 29 per cent price gain at the close of trading. The shares ended at 90 US cents, 20 cents up from the initial offer price of 70 cents on a turnover of about 3.05 million shares. A Hong Kong dealer said mainlanders' buying of the shares through unofficial channels was a reason for the relatively strong support, but the reception was lukewarm compared with previous B-share issues. B shares are meant for foreigners only but Chinese with foreign currencies have been buying this issue and other B-share stocks for some time. Yuan Yonglin, general manager of the manufacturer of plush and flannel, said: ''We are confident that the China market for plush and flannel will grow and that the prospects for our company will be bright.'' He said plans were afoot to co-operate with overseas specialists to develop new plush materials to expand the company's variety. The private placement of 35 million B shares, underwritten by Shanghai Shenyin Securities and co-ordinated by Sun Hung Kai International, was completed on November 27. Net proceeds came to about US$23 million. The combined total raised from A and B issues was 283 million yuan (about HK$379 million at the official rate), which will be used to finance the establishment of related joint ventures in Shanghai and abroad. Shanghai Haixin, one of the largest producers of plush in China, has 20 per cent of the market. Almost all the company's output is sold for foreign currencies.