Understanding that it's the details that make the difference between good design and exceptional design we created our keyboard series. The RRKB61W features our exclusive Z-Lock Foam System that allows you to customize the inner length, width and height ( length adjustable from 38" to 44", depth from10.5" to 16.5", height from 3" to 5.5) of your case to accommodate virtually any model of Roland, Yamaha, Korg, EM-U and other 61 key keyboards. Simply lock or un-lock the layers of Z-lock foam to create your perfect custom fit. And for sleek, stealth mobility we equipped each case with our unique low-profile wheels. Upgrade your keyboard not your case.