With due consideration, I went with 9.5in coil for my prizm

[PrizmIV]

I found one for very ChEaP!!! And, I bought it

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=5774975313&rd=1&sspagename=STRK:MEWA:IT&rd=1

 

Amazon Forum Fav 👍

Minelab PRO-FIND 35 Waterproof Pinpointer Metal Detector for Experts with Tone ID & Adjustable Sensitivity - Grab it through Amazon!

[Mona Lisa]

I put a 9.5 on mine and really like it. It's a lot easier to pinpoint with the hole in the middle. It detects deeper, too.