Hi guys. Found some info on the ultrasonics on the mowbot site. http://www.idx.com.au/~deverett/mowbot/ultrhard.htm Cheers! -- Eric van Es | Cape Town, South Africa mailto:vanes@ilink.nis.za | http://www.nis.za/~vanes LOOKING FOR TEMPORARY / HOLIDAY ACCOMODATION? http://www.nis.za/~vanes/accom.htm