The 159B-RTWX replacement tips for 159B-RTW contain two tips and 4 screws. Acetal has outstanding resistance to chemicals and solvents. These Acetal tips are electrically insulative and resistant to temperatures up to 185°F. The bodies are made of anti-magnetic Neverust® stainless steel (AISI 316L). The screws are flat-head 1/8" undercut (0.137" Dia.)(0.031" Hgt)(Drive Size No. 0)(42 threads per inch. Excellent for cleanroom applications and for avoiding the marring or scratching of items being handled.