diff --git a/src/userland/scisi/include/scisi.h b/src/userland/scisi/include/scisi.h
index bf97eb1..a7bb832 100644
--- a/src/userland/scisi/include/scisi.h
+++ b/src/userland/scisi/include/scisi.h
@@ -43,4 +43,20 @@
     uint8_t restData[127];
 } InquiryResponse;
 
+typedef struct {
+    uint32_t size;
+    uint8_t operationCode; // 0x25
+    uint8_t obsolete;
+    uint32_t LBAObsolete; // set to 0, must be inserted with MSB first.
+    uint16_t reserved;
+    uint8_t PMIObsolete;
+    uint8_t control;
+} ReadCapacity10Command;
+
+typedef struct {
+    uint32_t size;
+    uint8_t lastLBA[4]; // most significant byte first
+    uint8_t blockSize[4]; // most significant byte first
+} ReadCapacity10Response;
+
 #endif
\ No newline at end of file

diff --git a/src/userland/scisi/include/scisi.h b/src/userland/scisi/include/scisi.h
index bf97eb1..a7bb832 100644
--- a/src/userland/scisi/include/scisi.h
+++ b/src/userland/scisi/include/scisi.h
@@ -43,4 +43,20 @@
     uint8_t restData[127];
 } InquiryResponse;
 
+typedef struct {
+    uint32_t size;
+    uint8_t operationCode; // 0x25
+    uint8_t obsolete;
+    uint32_t LBAObsolete; // set to 0, must be inserted with MSB first.
+    uint16_t reserved;
+    uint8_t PMIObsolete;
+    uint8_t control;
+} ReadCapacity10Command;
+
+typedef struct {
+    uint32_t size;
+    uint8_t lastLBA[4]; // most significant byte first
+    uint8_t blockSize[4]; // most significant byte first
+} ReadCapacity10Response;
+
 #endif
\ No newline at end of file
diff --git a/src/userland/scisi/main.c b/src/userland/scisi/main.c
index 016c531..640195f 100644
--- a/src/userland/scisi/main.c
+++ b/src/userland/scisi/main.c
@@ -25,10 +25,22 @@
     
     printf("response: type: %x, removable: %i, version: %x, responseData: %x, additionalLength: %i\n",
             response->type, response->removable, response->version, response->responseData, response->additionalLength);
-    for (uint32_t i = 0; i < 10; i++) {
-        printf("restData: %x %x %x %x\n", response->restData[4*i], response->restData[4*i+1],
-                                                response->restData[4*i+2], response->restData[4*i+3]);
-    }
+}
+
+uint64_t getSize(ScisiDevice *device) {
+    ReadCapacity10Command *command = malloc(sizeof(ReadCapacity10Command));
+    command->size = sizeof(ReadCapacity10Command) - sizeof(uint32_t);
+    command->operationCode = 0x25;
+    command->control = 0;
+
+    request(device->serviceId, device->outFunction, device->out, U32(getPhysicalAddress(command)));
+
+    ReadCapacity10Response *response = malloc(sizeof(ReadCapacity10Response));
+    response->size = sizeof(ReadCapacity10Response) - sizeof(uint32_t);
+    request(device->serviceId, device->inFunction, device->in, U32(getPhysicalAddress(response)));
+    uint32_t blockSize = response->blockSize[0] << 24 | response->blockSize[1] << 16 | response->blockSize[2] << 8 | response->blockSize[3];
+    uint32_t maxLba = response->lastLBA[0] << 24 | response->lastLBA[1] << 16 | response->lastLBA[2] << 8 | response->lastLBA[3];
+    printf("max lba: %x, block size: %x\n", maxLba, blockSize);   
 }
 
 int32_t registerDevice(uint32_t in, uint32_t out, uint32_t serviceName, uint32_t serviceId) {
@@ -42,6 +54,7 @@
     listAdd(&devices, device);
     printf("registering a new SCISI device (in: %x, out: %x)\n", in, out);
     doInquiry(device);
+    uint64_t size = getSize(device);
     return 0;
 }