Cov lus piav qhia luv luv:

Extension springs muab tsis kam rau lub zog rub. UNION tsim cov kev cai tsim tawm kev tawm suab uas ntev ... thiab txhim khu kev qha - rau koj cov lus qhia tshwj xeeb. Springs nrog xaus uas yog hooked, looped los yog nrog cov duab tshwj xeeb - peb tau nruab nrog cov thev naus laus zis nyob rau hauv uas feem ntau kawg teeb tsa tau tsim nrog tsuas yog ib tus txheej txheem.