54mm

http://poweradaptermall.com/mk2431gah-18-zifpata-240gb-toshiba-mk2431gah-hard-drive-hdd-p-17515.html MK2431GAH 1.8" ZIF/PATA 240GB Toshiba MK2431GAH Hard Drive HDD TOSHIBA MK2431GAH Data Storage Physical Per drive, formatted1 240GB Number of Platters 2 Areal Density (max) 344Gb/in2 Data Transfer Rates Interface Transfer Rate 100MB/sec Media Transfer Rate (max) 488Mbps Other Average Seek Time 15ms Energy Consumption Efficiency 0.0013W/GB Rotational Speed 4200rpm Interface Prallel ATA (PATA) Buffer 8MB Physical & Environmental Specs Dimensions/Weight Height 0.31" (8mm) Width 2.13" (54mm) Depth 2.79" (71mm) Weight 2.08 oz (59g) Shock Operating Shock 4,900 m/s2 (500G/2.0ms) Non-Operating Shock 14,700 m/s2 (1,500G/1.0ms) 　 MK2431GAH run in Apple macbook air Rev A. (1st) video