She laid a spring mattress under the sheet.
她在床单下面铺了一个弹簧床垫。
Three to listen to: that is, to detect the spring mattress quality measures.
三听：即检测床垫中弹簧质量的措施。
The mattress has lost its spring.
那个床垫失去弹性了。
Purpose: it is suitable to all kinds spring soft mattress.
垫耐久性测试仪用途：本机适用于各种弹簧软床垫测试。
Purpose: it is suitable to all kinds spring soft mattress.
垫耐久性测试仪用途：本机适用于各种弹簧软床垫测试。
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