Industrial-grade stard SBR block, with high precision linear bearing inside. Surface silver plating treatment, beautiful anti-rust, hardness can as high as HRC62, me durable. The adjusting hle can adjust the tightness of the slider. Stardized processing, perfect f guide rail positioning. Perfect f your DIY CNC routers, mills, lathes. Aluminum alloy suppt rail with pre-drilled holes f ease of mounting. Type: Linear slide guide Glide path: linear guide Rated dynamic load: 860 Rate static load: 1370 Precision grade: H Fixed size: 8 (mm) Fixed mode of sliding block: Locking type Allowed static tque: 1 (kn.m) Weight:1050g colour:Silver Material:metal size: Linear Slide Rails- 500mm / 19.7inch (Length) x 12mm / 0.47inch (Diameter); Linear Bearing Side Blocks -40mm x 40mm x 28mm/1.57 x1.57 x1.10inch( Length x Width x Height) Package Contents: 1 x linear guide 2 x Linear bearing slider Only the above package content, other products are not included. Note: Light different displays may cause the col of the item in the picture a little different from the real thing. The measurement allowed err is 1-3cm.