DESCO Statfree i 40930 Black Rubber Conductive Interlocking Floor Mat, 36" Length x 24" Width x 0.50" Thick Premium nitrile butadiene homogenous rubber with no clay or silica fillers: Superior durability and electricals provides value, long life without discoloring and delamination Ergonomic design dome/support cell structure; suspended bounce feel, and matrix of "tri-radial" supports firming up as weight is applied improves worker comfort and productivity Tested for cleanrooms; minimal particulation suitable for use in critical environments; used in class 1000 cleanrooms Individual mats should be grounded; Linked mats should be grounded 10-12 feet Lead-free RoHS compliant