[Plugin: Contact Form 7] Set Width of Drop Down

How do I Set Width of Drop Down
its only showing 20 spaces horizontally
need like 100-150 this is my code

<p>Install options -Check multiple if needed (required)
[select* options multiple include_blank “phpBB3 Install: $8.00” “phpBB3 Upgrade 1 version: $10.00” “phpBB3 Modification install $8.00 – $50.00 Depends on how complex” “1 year upgrades on installs of Mods – $25 plus price of Mod install” “Stargate Portal Upgrade Install from Previous Version – $40” “Stargate portal installs w/ no mods previously installed – $20” “Stargate portal installs w/ mods previously installed – $40” “Stargate Portal Install w/ phpBB3 new install – $30” “phpBB Style / Theme Install – $15” “phpBB / Stargate Portal Style / Theme Install – $25”] </p>

This is what it looks like