Replacement travel pack battery for HP Compaq 6530b, 6730b, 6735b, 8510w, 8710w, nc6230, nc6320, nc6400, nx7400, tc4400 Tablet PC; Elitebook 6930p, 8440p, 8540p; Probook 6440b, 6450b, 6540b, 6550b