of fire, in most cases limited only by the mechanical capabilities of the marker itself. Due to the large number of aftermarket upgrades available, the Ion can be customized or used stock to hold its own in today's fast-paced speedball tournaments. It can also easily be made into a competent woodsball marker. Operation Internally, the Ion features a spool-valve design, similar to a Shocker SFT or a Dye Matrix. However, the operation of the Ion is somewhat simpler than a Shocker SFT or Matrix in that it does not use a 4-way solenoid valve. The Ion's solenoid valve only has three hoses: one to provide air to the solenoid, one to provide air to a reservoir chamber behind the bolt, and the other which provides air to the front of the bolt to hold it back while the marker is at rest. The solenoid thus directs air either to the front of the bolt when not firing, or to the air reservoir behind the bolt, to blow it forward. When the Ion is fired, the air in front of the bolt that holds it back is drained back through the solenoid, which causes the air in the rear of the firing chamber to blow the bolt forward. In order to expedite the draining of air from the front of the bolt, many users add a quick exhaust valve (QEV) to their marker. The QEV replaces a fitting on the Ion's body and allows the draining air to vent into the body cavity instead of passing all the way back through the solenoid. By allowing the air to vent faster, this allows the bolt to close faster and with more force, which permits lower operating pressure and dwell (the time the solenoid valve is open). The QEV also acts as a trap for excess grease that might otherwise enter the solenoid and cause problems. Two other markers manufactured by Smart Parts, the SP-8 and the Epiphany, are based on the Ion's spool-valve design. References External links Smart Parts website Smart Parts Ion Review at About.com Ion Technical Guide Paintball markers