UEI Plc is making a $10.50 a share tender offer for Kevex Corp, its biggest US competitor in the field of materials analysis instruments: the bid values the company at $56m and UEI reckons that with Kevex, which did $1.5m pre-tax on sales of $36.4m in the year to July, it would have $60m to $70m of a world market totalling $200m to $250m; it says that writing off goodwill will take its gearing soaring to about 115%, but that it should fall to 60% by the end of January 1989.