suitable for KS3+. Six screen mesh sizes (see below for further details) will let students separate and grade soil and rock samples in order to determine the make-up of soil strata. Set includes bottom pan and lid with Teacher's Guide. Sieves external diameters 18cm. Screen mesh sizes: #5 mesh - 0.151" opening - medium and large gravel will not pass. #10 mesh - .0725" opening - small gravel will not pass. #35 mesh - .0173" opening - coarse sand will not pass. #60 mesh - .0092" opening - coarse and medium sand will not pass. #120 mesh - .0047" opening - very fine sand will not pass. #230 mesh - .0029" opening - fine sand will not pass, only very fine sand, silt and clay.