A wheel or Cast­er is the low­est part of chair, which gives mobil­i­ty­to the chair.  Typ­i­cal­ly in fur­ni­ture indus­try we use twin type pin cast­ers 50mm diam­e­ter 2.Casters are of two types:

• PP cast­ers- These Cast­ers are made of polypropy­lene (PP) mate­r­i­al. Cast­ers made from PP are hard ones, hav­ing rel­a­tive­ly faster move­ments.
• PU cast­ers- These Cast­ers are made of polyurethane (PU/PUR) mate­r­i­al which is soft in nature. It has many advan­tages over PP  wheels such as :

i. Noise Reduc­tion
ii. Resis­tance to cor­ro­sion
iii. Heavy load capac­i­ty
iv. Soft­ness of move­ment
v. Dura­bil­i­ty

These are the mould­ings made for sta­bil­i­ty and move­ment of chair. Usu­al­ly fur­ni­ture indus­try uses 5 prone bases. There are vari­ety of bases accord­ing to diam­e­ter and mate­r­i­al of Base.

• PP Base — These Bases are made of Polypropy­lene mate­r­i­al. These are  cheap­est one but very embrit­tle (can be break any time, not rec­om­mend­ed). PP bases have poor resis­tance to UV, impact and scratch­es.
• Nylon Base — These are made of nylon mate­r­i­al and have high­est qual­i­ty. Nylon bases are very well rec­om­mend­ed.
• Met­al Base — These are made from sheet met­al or met­al tubes. As a met­al it has good sta­bil­i­ty and long life pro­vid­ed it is for, brand­ed sup­pli­er.
• Chrome Base-These are the met­al bases hav­ing chrome plat­ing.
• Alu­mini­um Base –These bases made from alu­mini­um cast mate­r­i­al.  These are used usu­al­ly high end chair, as it is cost­ly.

Also known as  office Chair Pneu­mat­ic Gas Cylin­der.

• Class 3 — This heavy duty pneu­mat­ic gas cylin­der is typ­i­cal­ly installed on exec­u­tive and mul­ti-func­tion man­age­r­i­al chairs.
• Class 4 — Typ­i­cal­ly installed on chairs rat­ed up to 350 lb. 4” stroke (seat trav­el from low­est to high­est settings)this heavy duty pneu­mat­ic gas cylin­der is typ­i­cal­ly installed on exec­u­tive and mul­ti-func­tion man­age­r­i­al chairs

Office Chairs have dif­fer­ent types of mech­a­nisms to revolve, move, and tilt the upper part of the Chair. The major mech­a­nisms used in office chairs are: Push Back Mech­a­nism, Tilt­ing Mech­a­nism, Syn­chro Mech­a­nism, and few more.

• Tilt/Pushback — Tilt­ing mech­a­nism used in office chairs is where the seat, arm­rests and back­rest are one piece. When you lean back the whole chair tilts. It is there­fore not pos­si­ble to move the seat and back inde­pen­dent­ly of each oth­er.
• Pneu­mat­ic Seat Height Adjust­ment — A pneu­mat­ic cylin­der is attached to the chairs mech­a­nism locat­ed under the seat cush­ion. This cylin­der allows for quick and easy adjust­ment through­out a spec­i­fied height range. This adjust­ment is often accom­plished through the use of a knob locat­ed under­neath the seat cush­ion on either the right or left side to the chair.
• Tilt Lock — once a chair is locked in a tilt posi­tion it can­not be unlocked until the user reclines or tilts back a few degrees fur­ther reliev­ing pres­sure from the knob so that the chair may be reset back to the orig­i­nal posi­tion.
• Tilt with any posi­tion lock­ing — The tilt ten­sion adjust­ment is mod­i­fied by turn­ing a usu­al­ly knob found under­neath the seat.The tilt ten­sion knob will increase or decrease the amount of force need­ed to make the chair rock or recline back­ward. Usu­al­ly, sev­er­al turns of the tilt ten­sion knob are required to loosen or tight­en the ten­sion to a notice­able lev­el.
• Syn­chro­nous — The syn­chro­nous mech­a­nism (syn­chro tilt) com­bines a move­ment of the back­rest and a cor­re­spond­ing small­er move­ment of the seat. The move­ment of the back­rest is there­by larg­er than the move­ment of the seat.
• Syn­chro­nous with any posi­tion lock­ing — The syn­chro­nous mech­a­nism

(syn­chro tilt) com­bines a move­ment of the back­rest and a cor­re­spond­ing small­er move­ment of the seat. The move­ment of the back­rest is there­by larg­er than the move­ment of the seat. The only dif­fer­ence is in, Syn­chro­nous with any posi­tion lock­ing we can lock the posi­tions using knob.

• Fixed –

1] PP – This han­dles are made of polypropy­lene mate­r­i­al. PP han­dles are very rough in touch.

2] PU – This han­dles are made of polyurethane material.PP han­dles are very soft in touch. Rec­om­mend­ed for sin­gle user chair.

• Adjustable – This han­dles may have PP or PU pad. Such han­dles are adjustable in height, as per user com­fort. Pads used in this type of  han­dles may have lat­er­al or hor­i­zon­tal move­ment.

Usu­al­ly, seat con­tains ply or foam cov­ered with cloth. Seat comes in two types-

• Mesh — Mesh has become a very pop­u­lar mate­r­i­al for office chairs. Mesh office chairs typ­i­cal­ly come in an ergonom­ic shape to pro­vide sup­port for the back. These types of chairs may have a cush­ioned seat or a mesh seat. Over time, a mesh chair may lose its shape, so it is best to pur­chase office chairs with a high-qual­i­ty mesh mate­r­i­al. Mesh is very breath­able, but some mesh mate­ri­als have been known to irri­tate the skin.
• Cush­ion — A cush­ion is made from mul­ti­ple types of mate­r­i­al and in mul­ti­ple shapes that pro­vides com­fort when sit­ting or lying down. Most cush­ions are filled with foam or some oth­er poly mate­r­i­al depend­ing on how much com­fort the man­u­fac­tur­er is look­ing for. Cush­ions may be used for sit­ting or kneel­ing upon, or to soft­en the hard­ness or angu­lar­i­ty of a chair or couch.

Ply­wood is a mate­r­i­al man­u­fac­tured from thin lay­ers or "plies" of wood veneer that are glued togeth­er with adja­cent lay­ers hav­ing their wood grain rotat­ed up to 90 degrees to one anoth­er. It is an engi­neered wood from the fam­i­ly of man­u­fac­tured boards which includes medi­um-den­si­ty fibre­board (MDF) and par­ti­cle board (chipboard).compressed ply­wood ergonom­i­cal­ly design to give prop­er sit­ting com­fort to the chair.

• STA
• Metro-medi­um
• Twin
• Met­rics

We can use spe­cial­ly mould­ed foams as per required design or soft foam
avail­able in mar­ket. For com­fort­able sit­ting pre­de­fined foam shapes are used for 45 or 55 den­si­ty and it is rec­om­mend­ed. Spe­cial­ly mould­ed foam such as –

• STA
• Metro-medi­um
• Twin
• Met­ric
• PU Foam – This foam is soft, its den­si­ty varies from 20 to 50 as per
  require­ment.

Fab­ric is anoth­er mate­r­i­al that could poten­tial­ly irri­tate the skin, but it is very
breath­able. Fab­ric office chairs may be very com­fort­able to sit in at first, but over time the cush­ion­ing and fab­ric mate­r­i­al will even­tu­al­ly begin to break down.