The Akiles CoilMac-ER spiral binding machine is available in two different models, including a standard version and a plus version. The standard model features five punching pins that can be disengagead, but all of the pins on the plus model can be disengaged, for fully customizing and punching pattern control. In addition, the standard model features the standard 4mm round holes, whereas the ER-plus machine has slightly oval holes, measuring 4mm x 5mm, which makes for easier coil inserting. Lastly, the hole spacing is very slightly different for the ER and ER+ machines; the standard model has basic 4:1 pitch, 0.250" spacing, but the plus model features an advanced 4:1 pitch, 0.248" spacing that has been formulated specifically for 44 perfect holes on a letter size 8 1/2" x 11". When you buy the Akiles CoilMac-ER spiral binding machine online, you get a low to mid-volume machine with a unique feature: an attached mini coil inserter. The small inserting machine offers some of the convenience associated with a higher volume machine, but at a lower cost and for smaller volumes.