New construction frame-in with collar for pre-wiring and easier layout planning.. . Compatible Fixtures:. NIOC-4RNB: 4" Iolite Can-less Round Bullnose. NIOC-4RNDC: 4" Iolite Can-less Round Downlight. NIOC-4RPH: 4" Iolite Can-less Round Pinhole. NIOC-4RSLA: 4" Iolite Can-less Round Adjustable Slot. NIOC-4SNDSQ: 4" Iolite Can-less Square Downlight