The goal of this study is to conduct a pilot randomized waitlist-controlled trial to assess the feasibility, acceptability, and preliminary effects of substituting the NIDA standardized research e-cigarette (SREC) for combusted cigarettes in MOUD-TUD who are not ready to quit smoking. A waitlist controlled RCT using a mixed-methods sequential explanatory design will investigate the impact of SREC provision on: 1) tobacco use behavior (e.g., cigarettes per day \[primary outcome\], SREC use), 2) biomarkers (e.g., carbon monoxide, anabasine), 3) cigarette dependence and withdrawal, and 4) short-term health effects and tolerability (e.g., respiratory symptoms, substance use). In the proposed RCT, N=40 adults stable on MOUD with buprenorphine who report daily smoking recruited from MGH primary care practices will be randomly assigned to receive the SREC for 8 weeks, either immediately (iSREC), or after an 8-week delay (waitlist control \[WLC\]). They will be followed an additional 4 weeks after SREC provision ends (to 12 weeks in iSREC and 20 weeks in WLC).