I have a nitrous express bottle volume gage...the directions arent very good...cant really find anything on the internet for it either....this is the gage

http://cgi.ebay.com/ebaymotors/_Car-Truck-Parts-Accessories__NX-Nitrous-Express-15534-Nitrous-Bottle-Volume-Gauge_W0QQitemZ370085557647QQadnZCarQ20Q26Q20Truck Q20PartsQ20Q26Q20AccessoriesQQadiZ2865QQcmdZViewIt em?hash=item370085557647&_trkparms=72%3A543%7C39%3A1%7C65%3A12%7C240%3A1318&_trksid=p4506.c0.m245

Thanks guys any help would be awesome