Countersunk hlau nplaum yog tsim los ntawm ntau yam ntaub ntawv, feem ntau suav nrog sintered NdFeB thiab ferrite. Sintered NdFeB hlau nplaum yog nyiam rau lawv cov khoom siv hluav taws xob siab thiab cov khoom sib nqus zoo heev, thiab tau siv dav hauv cov ntawv thov kom muaj zog sib nqus. Ferrite hlau nplaum, ntawm qhov tod tes, yog siv rau hauv cov ntawv thov uas tsis tas yuav muaj zog sib nqus, tab sis ntev - lub sijhawm ua haujlwm ruaj khov yog qhov tsim nyog, vim lawv cov nqi qis thiab zoo corrosion kuj.