A height of cut adjuster for a reel mower cutting unit with a removable attachment includes a front roller with a shaft positionable in front of the cutting reel axis, and a roller bracket assembly having a bottom bracket removably attached to a top bracket to provide a gap therebetween where the front roller shaft is held. The roller bracket assembly may be pivoted, and the top bracket may be connected to the bottom bracket in a different position further from the cutting reel, so that an attachment such as a conditioner may be installed between the front roller and the cutting reel.