Help on crank sizing please...

[Howser]

Hi - I'm after some advice on the sizing of cranks please. Probably a silly question to ask but just wanted to make sure I buy the right ones to fit the bike I am building -  which you've probably worked out is my first build   

I'm looking at one piece cranks and understand the length sizes but what does the numbering 28t and 24t stand for?  Most seem to be 28t but I've seen some 24t. Not sure what the difference is and what ones would fit my bike, which is an 84 mongoose Californian.

Also - can anyone please help me with the type/size bottom brackets do I need to look out for to go with the bike?

Any help or advice would be very much appreciated 

Many thanks

[Hootski70]

tpi stands for threads per inch , most one piece cranks and bottom brackets  are 24tpi  ,older mongoose on the other hand are 28 tpi , hope this helps .

[Howser]

Thanks and that makes sense. Sounds like i should be ok providing I keep to the same numbering for both crank and bb.

Cheers for the advice