Abstract: A reclining member of seat backs is revealed. The reclining member is arranged on center of a seat bracket. The reclining member includes locking slots on an adjustment rod and locating pin that lock with each other so as to make the seat back become a stable and positioned state after the reclining angle of the seat back being adjusted. Thereby users feel smooth and comfortable while reclining the seat back.

Abstract: An elastic waist support is installed between a back frame and a mesh member of a chair, and can be adjusted in height; the back frame consists of a front frame part, and a rear frame part, which are firmly joined together; the mesh member covers a front side of the front frame part with a periphery thereof being sandwiched between the front and the rear frame parts; the back frame has two opposite supporting extensions protruding from inward sides of two longitudinal portions thereof; each of the supporting extensions has a guiding groove thereon; the waist support has two joining protrusions thereon, and it is joined on the back frame with the joining protrusions being respectively embedded in the guiding grooves.

Abstract: A chair seat includes an upper metallic covering sheet, a lower covering sheet, and a main body; the upper metallic covering sheet is substantially in the shape of a bivalve shell valve, and the main body is held in the upper metallic covering sheet; the upper metallic covering sheet is pressed at a lower circumferential portion thereof to form a compressed step-shaped section, which closely touches and grips the main body; the lower covering sheet is substantially in the shape of a bivalve shell valve, and has a holding portion, and the upper metallic covering sheet is tightly fitted in the holding portion of the lower covering sheet at the compressed step-shaped section such that the main body is wrapped, and such that the upper metallic covering sheet is separable from the lower covering sheet for replacement.

Abstract: A chair seat and back structure includes a loop-shaped part with a space encompassed by an inner edge thereof, and an elastic covering part; the loop-shaped part has a curvature and a loop-shaped holding groove near to a circumferential edge thereof; the covering part positioned over the loop-shaped part, in tension and with a circumferential edge thereof being passed into the loop-shaped holding groove and secured to the loop-shaped part; therefore, the covering part will be changed in the shape by the sitter's body curvature, and the sitter's body will touch the chair with increased area.

Abstract: A chair back includes a waist support, a board-shaped part, and a mesh member; the board-shaped part has guide grooves on a front side; the mesh member includes a frame, and a mesh secured over a space encompassed by the frame; the mesh member is secured right in front of the board-shaped part; the waist support is sandwiched between the mesh member and the board-shaped part with such a tightness that it can be moved up and down for adjusting position; the waist support has guide protrusions on a rear side thereof, which are fitted in the guide grooves of the board-shaped part; the waist support has two grip portions extending from two ends thereof and sticking out from two lateral edges of the chair back such that the sitter is allowed to adjust the waist support by means of exerting force on the grip portions.