(Reuters) - Two blank-check firms backed by SoftBank Group Corp are aiming to raise a total of about $550 million in their initial public offerings, regulatory filings showed on Friday. Special purpose acquisition company (SPAC) SVF Investment Corp 2 said it would sell 20 million units, comprising shares and warrants, priced at $10 apiece in its IPO. SVF Investment Corp 3 said it would sell 35 million shares at the same price. here SoftBank has tried to ride the mania for SPACs, with a blank-check backed by the Japanese conglomerate’s Vision Fund’s managers - SVF Investment Corp - raising $604 million earlier this year. Another SPAC headed by the company’s Chief Operating Officer Marcelo Claure is aiming to raise $200 million. Even office-sharing startup WeWork is in talks to go public through a merger with a blank-check firm, a source said last month. A SPAC, a shell company that raises money in an IPO before later merging with a privately held company to take the latter public, has become many investors’ structure of choice over the past year. Another SPAC headed by the company’s Chief Operating Officer Marcelo Claure is aiming to raise $200 million. Even office-sharing startup WeWork is in talks to go public through a merger with a blank-check firm, a source said last month. A SPAC, a shell company that raises money in an IPO before later merging with a privately held company to take the latter public, has become many investors’ structure of choice over the past year.