I'm not afiliated with DBM scientific 1 800 800 3668 (phone) but they have excellent tips for p20 p200, etc for under $70 per 1000. C. Neal Stewart, Jr. Crop and Soil Sciences Department University of Georgia Athens, GA 30602-7272 Email: NSTEWART at UGA.CC.UGA.EDU Voice: (706) 542-0924 or -0919 FAX: (706) 542-0914