Are other needle/tip sizes available?

Yes, there are various size tips that are available.  

Included with the sprayer:

• 1.5mm (Blue)-Fine finish atomization.  Stains, water base finishes, and polyurethane.   
• 2.0mm **(Pre-installed)**(Green)-Fine finish atomization.  Latex paint, chalk paint, milk paint, varnishes, polyurethane, and oil based paints.
• 4.0mm (Red)-Medium/Coarse finish atomization.  Primer and latex paint.  

Available separately as a kit:

• 1.0mm (Orange)-Fine finish atomization.  Sealers, varnish, and water base finishes. 
• 2.5mm (Yellow)-Medium finish atomization.  Latex paint, chalk paint, and milk paint.
• 3.5mm (Black)-Medium finish atomization.  Primer and latex paint.