Water-saving sheet and water-saving device having the same

A water-saving sheet, including:

• a sheet body, including a central assembling base and a plurality of through holes arranged around the central assembling base, a circumference of the sheet body radially protruding outward to form an engaging flange structure and having a material-reduced structure near the engaging flange structure, the engaging flange structure for being positionably engaged with an inner wall of a tube;
• an elastic ring, annularly arranged on the central assembling base and being at least partially located correspondingly above the plurality of through holes, the elastic ring and the central assembling base forming at least one first passage therebetween which is communicable with the plurality of through holes, the elastic ring and each said through hole forming a second passage therebetween which communicates with each said through hole;
• wherein the engaging flange structure includes three wedge-shaped protrusions arranged equiangularly and spacedly, each protrusion has a top face and a bottom face, the top face is substantially parallel to a radial direction of the sheet body, the bottom face is unparallel to the top face and faces outward;
• wherein the material-reduced structure is an annular groove, the annular groove has an inner fringe and an outer fringe, the inner fringe is closer to a center of the sheet body than the outer fringe is, a distance between the circumference of the sheet body and the inner fringe of the annular groove is defined as D1, a distance between the circumference of the sheet body and the center of the sheet body is defined as D2, D2 is more than six times D1, a radial width of the annular groove is defined as W1, W1 is 0.5-0.80 times D1, the through holes are surrounded by the inner fringe of the annular groove.