# Diameter [GstarCAD 2027](Help%20System/GSTARCAD/2027/Index.md) → [What's new](Help%20System/GSTARCAD/2027/What's%20new/(What's%20new).md) ## Function Description: Creates a diameter constraint parameter for a circle, arc, or polyline arc segment. ## Command Access: Icon:  Menu Item: / Ribbon: Block Editor > Dimensional > Diameter Toolbar: / Command Line: BCPARAMETER > Diameter Command Alias: / ## Command Prompts: ``` Select arc or circle: ``` ## Operation Steps: 1、As shown in the figure, select the circle to add a diameter constraint parameter. 2、The diameter of the circle will be constrained.  --- [Original help](https://www.gstarcad.net/help/GstarCAD_2027_en-US/detail/GstarCAD2027NEW/GCR_BCPARAMETER_D.html) · © Gstarsoft Co., Ltd.