GC operand bundle allowed value types

What value types can I store in GC operand bundles? Is it limited only to pointers, or can other values be stored in the operand bundle as well (and thus be emitted to the stack map)?

For context, I would be manually generating statepoint calls in this case (not using RS4GC).

Operand bundles in general can get any value type that are allowed to be sent to an ordinary function as arguments. There could be custom operand bundles that impose their own restrictions on the operands.