Which collateral types can be posted?

Borrowers are able to access undercollateralized & unsecured Bitcoin loans on Zest Protocol. Pool delegates will assess loan requests and agree borrower rate and collateralization ratios with borrowers. Prior to withdrawing funds, borrowers will be required to deposit the agreed collateral to their loan vault. This collateral will be released after final repayments are made.
Collateral is a SIP-10 token.